Chronic perinatal pain as a risk factor for postpartum depression symptoms in Canadian women.

Gaudet, Caroline ; Wen, Shi Wu ; Walker, Mark C. 等

Postpartum depression (PPD) is a mood disorder that can occur after childbirth. Using the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders, PPD is classified as a major depressive disorder with a "peripartum" onset specifier if symptoms occur during pregnancy or within 4 weeks postpartum. (1) However, research demonstrates that PPD onset can be anywhere from pregnancy to late postpartum. (2,3) PPD can be a challenge to detect as its symptoms are similar to normal consequences of childbirth. (4) It is therefore unfortunately often missed by clinicians, and many women may remain undiagnosed. (5) Mothers who are diagnosed with PPD may not be treated as adequately as others receiving treatment for depression. (5) Left untreated, PPD can result in important and pervasive consequences. Depressed mothers are less likely to return to their pre-pregnancy levels of function, partners of depressed mothers may have difficulties adjusting, and their children may have poorer health outcomes. (6-8)

There is a wide range of estimates of PPD due to the varying methodologies and PPD definitions used in research. (2) The most widely reported prevalence of PPD is 13%.9 However, a recent systematic review reveals that the prevalence of depression (minor and major) at three months after childbirth could be as high as 19.2%. (10) Data from the Maternity Experience Survey reveal that the national prevalence of PPD symptomatology (undiagnosed PPD) in Canada is approximately 8.7%, and varies from province to province ranging from 5% in New Brunswick to 15.9% in the territories. (11)

The aetiology of PPD is complex. Many psychological, psychosocial, socio-economic and obstetric risk factors have been reported to be associated with this disorder. Meta-analyses revealed that the psychological and psychosocial risk factors such as prenatal depression, stress, anxiety, and low social support are among the strongest risk factors for PPD. (9,12,13) It is surprising that these reviews do not identify pain as a risk factor for PPD as the association between pain and depression is well known and consistently observed across a variety of diagnostics. (14) Evidence suggests that the association between pain and depression could be of a causal nature. (14)

[FIGURE 1 OMITTED]

There are three main causal hypotheses to describe the nature of the pain-depression association. In the "antecedent" hypothesis, depression precedes and causes pain whereas in the "consequence" hypothesis, pain precedes and causes depression. (14) The third hypothesis is the "scar" hypothesis according to which "episodes of depression occurring before the onset of pain predispose to a depressive episode after pain onset". (14) Of all three hypotheses, the "consequence" and "scar" hypotheses are the most supported by evidence while the antecedent hypothesis is mainly refuted. (14,15)

The association between chronic pain and depression is thought to be universal. (14) However, it remains unknown whether chronic pain caused by pregnancy and childbirth is associated with PPD symptoms. The objective of this study was to examine whether pain caused by pregnancy and childbirth is an independent risk factor for PPD symptoms in a nationally representative sample of Canadian women.

METHODS

We received ethics approval from the Ottawa Hospital Research Ethics Board to perform secondary data analyses of the Canadian Maternity Experiences Survey (MES), a cross-sectional study conducted by Statistics Canada on behalf of the Public Health Agency of Canada in 2006.16 The MES population included 6,421 respondents who represented a total of 76,508 puerperal Canadian women. (16) Respondents were "birth mothers 15 years and older who had a singleton live birth in Canada, between February 15, 2006 and May 15, 2006 in the provinces or between November 1, 2005 and February 1, 2006 in the territories and who lived with their infants at the time of data collection". (16) The survey was conducted at an average of 7.3 months postpartum (range: 5 to 14 months postpartum).17 Data were collected through computer-assisted telephone interview (CATI) in the provinces and territories, and through in-person interviews in the territories when it was not possible to do the survey by phone. (16)

The outcome of interest was a positive screen for PPD symptoms, defined as a score of 13 or higher on the Edinburgh Postnatal Depression Scale (EPDS).18 A score of 13 or higher on the EPDS is the recommended cut-off to use for identifying probable major depression postnatally. (18,19) The EPDS is a 10-item scale that has been validated for research and for use in the community to screen for PPD.18 It has a sensitivity of 86%, a specificity of 78%, and its positive predictive value is 73%. (18)

There were three exposures of interest pertaining to problematic perinatal pain: 1) the presence of problematic perinatal pain in the first three months postpartum, 2) the duration of problematic perinatal pain, and 3) the number of types of perinatal pain at the time of interview.

Presence of problematic perinatal pain in the first three months postpartum

The first exposure of interest was the presence of problematic perinatal pain in the first three months postpartum. It was a binary variable and was created with the respondent's answers to the MES questions about the experience of five types of problematic pain within the first three months postpartum (vagina, caesarean incision site, breasts, back, and severe headaches). For each of these types of pain, the respondents were asked: "during the first three months after the birth of your baby, how much of a problem was pain (in this body area)?" The choices of response were: 1) not a problem, 2) somewhat of a problem, and 3) a great deal of a problem. Answering "somewhat of a problem" or "a great deal of a problem" to any of the pain-related questions would classify a respondent as being exposed. (20)

Duration of problematic perinatal pain

The second exposure of interest was the duration of problematic perinatal pain. It was a three-level exposure variable: no pain, acute pain only, and chronic pain. Respondents who reported problematic perinatal pain in the first three months postpartum but no problematic perinatal pain at the time of interview were considered to have had acute pain only. Respondents who still reported problematic pain at the time of interview (range: 5-14 months postpartum) were classified as having chronic perinatal pain.

Number of types of perinatal pain at the time of interview

The third exposure of interest was the number of types of perinatal pain reported by the participants at the time of interview. The range was from 0 to 5. However, to comply with Statistics Canada disclosure control policy, categories with too few respondents were collapsed. This variable has four categories: 1) none, 2) one, 3) two, and 4) three or more.

Covariates

The covariates included in this study were selected from studies on the risk factors of PPD and pain. In order to ensure meaningful interpretation of the results, the variables were grouped according to three main categories: 1) socio-demographics, 2) obstetric and health, and 3) psychosocial and psychological factors. Please refer to Appendix A for more information on the covariates.

We assessed each risk factor for confounding. First, we compared prevalences of perinatal pain and PPD symptoms for respondents with the risk factor and for those without the risk factor. We then obtained and analyzed the crude odds ratio for the association between the risk factor and perinatal pain, and the risk factor and PPD symptoms. Confounding was suspected if the prevalence of pain and PPD symptoms were higher when the risk factor was present, and if the crude odds ratios were statistically significant for each association. Results from the confounding analyses are available in Appendix B.

A few selected variables were suspected effect modifiers and were analyzed for effect modification. These variables were: maternal nativity status, birthing method, sex of the baby, use of non-medical pain relief methods, use of medical pain relief, maternal body mass index, maternal smoking, and social support. The authors can be contacted for further information on the selection of these potential effect modifiers.

Figure 1 presents the study analytical plan. Analyses included full multivariate logistic regression models as well as six submodels that were fitted for each of the three main pain exposures of interest. The six submodels contained different combinations of the three groups of covariates (socio-demographic, obstetric/ health, and psychological/psychosocial) in order to assess the different impact of these three groups of variables on the association between perinatal pain and PPD symptoms. Unbiased weighted analyses were obtained using Statistics Canada's BOOTVAR program (version 3.1) and the bootstrap weights. (21) Multiple imputations by means of regression analysis were done using the IVEware Imputation and Variance Estimation software available online. (22) All logistic regression analyses were performed on SAS 9.2. (23)

A complete subject approach to the analyses was implemented. Due to incomplete information, 12.6% of the respondents were eliminated, resulting in a final sample size of 5,614. To address potential bias, sensitivity analyses were performed on a full multiply imputed dataset as well as in a subsample of respondents who were never previously depressed.

RESULTS

Descriptive statistics

Among the respondents included in the final analysis, 449/5614 (7%) screened positive for PPD symptoms. The characteristics of the MES respondents are described in Table 1.

Problematic perinatal pain in the first three months postpartum

Most of the respondents (4553/5614, 81.7%) reported problematic perinatal pain within the first three months postpartum. Among women who underwent caesarean section, incisional pain was the most common (927/1480, 62.6%). Among women who had a vaginal delivery, perineal pain was most commonly reported (2144/4134, 51.9%). Other common types of pain in the study population included breast pain (2819/5614, 50.5%), back pain (1915/5614, 35.5%), and severe headaches (556/5614, 10.4%).

Problematic perinatal pain at the time of interview

Twenty-seven percent (1468/5614) of the respondents reported problematic perinatal pain at the time of interview. Once again, caesarean incision pain was the most often reported problematic perinatal pain for women who had had a caesarean section (298/1480, 20.1%). The second most common, back pain, was reported by 16.1% (853/5614) of all respondents. Perineal pain was still present in 7.1% (294/4134) of women who had had a vaginal delivery. Severe headaches (174/5614, 3.3%) and breast pain (161/5614, 2.8%) were the least common types of pain at the time of interview.

Multivariate logistic regressions

Table 2 presents the results from the multivariate logistic regressions, as well as the sensitivity analyses.

Presence of problematic perinatal pain in the first three months postpartum

When all study variables were held constant, odds of screening positive for PPD symptoms for respondents who reported any problematic perinatal pain in the first three months postpartum were 1.7 (95% CI 1.2-2.5) compared to respondents who did not report problematic perinatal pain.

Duration of problematic perinatal pain

Compared to their counterparts who did not report any problematic perinatal pain, odds of screening positive for PPD symptoms for women who reported problematic perinatal pain in the first three months postpartum were 1.3 (95% CI 0.9-1.9) while the odds for those who reported problematic perinatal pain at the time of delivery were 2.4 (95% CI 1.6-3.6).

Number of types of perinatal pain at the time of interview

A dose-response association was observed between the number of types of perinatal pain at the time of interview and PPD symptoms, with increasing odds of screening positive for PPD symptoms with more types of perinatal pain. Odds of screening positive for PPD symptoms in respondents reporting one type of perinatal pain were 1.7 (95% CI 1.3-2.2) while the odds were 3.2 (95% CI 2.1-4.9) for respondents with two types of perinatal pain and 4.2 (95% CI 0.7-0.25) for respondents with three or more types of perinatal pain.

Only a few study variables remained independent predictors of PPD symptoms when all variables were included in the regression models. Along with the pain variables, the covariates that consistently remained independent predictors of PPD symptoms were: 1) maternal nativity status, 2) perceived stress, 3) number of past stressful life events, 4) lack of social support, 5) a history of depression, and 6) a history of abuse.

The results from the investigations into effect modifications are presented in Table 3. No statistically significant effect modification or biological interaction was found, although trends were observed. The association between problematic perinatal pain and PPD symptoms was stronger for respondents who were foreign-born, had had a caesarean delivery, were obese, reported having adequate social support, were non-smokers, and did not use any pain relief method.

The sensitivity analyses revealed that the final model estimates were robust. The estimates from the multiply imputed dataset were slightly higher than the estimates from the complete subject sample, suggesting that our final estimates are conservative.

DISCUSSION

In our study, problematic perinatal pain was strongly associated with PPD symptoms in a large representative sample of Canadian women. These findings are consistent with other studies that examined the association between various types of perinatal pain and PPD.

In a large study on 1,288 women who had vaginal and caesarean deliveries, acute pain at 36 hours postpartum was associated with both persistent pain and PPD at eight weeks after giving birth. (24) Lumbopelvic pain at three months postpartum was associated with PPD symptoms in a small cohort study, (25) and back pain at six months postpartum was associated with PPD symptoms (OR 2.2) in n Australian population-based study. (26) Finally, in a study on early breastfeeding experiences, women who experienced severe breastfeeding pain at one day, one week, and two weeks postpartum were more likely to be depressed at two months postpartum. (27)

One study reports findings suggesting that pain is a confounding factor in PPD screening. (28) PPD status at 8 weeks postpartum was not associated with postpartum pain measured between the 3rd and 5th day postpartum. (28) It is possible that pain measurements in the study were taken too early to capture the suffering associated with pain that becomes chronic, and this may explain why they did not find an association between postpartum pain and PPD. As Gatchel (15) explains, "one of the consequences of dealing with chronic pain is the development of emotional reactions such as anxiety and dysphoria produced by the long term "wearing down" effects and drain of psychological resources".

The design of this study does not allow for any conclusion regarding causality. However, this study does give important clues that merit further examination. The fact that the association between pain and PPD symptoms in the subsample of respondents who were never previously depressed was stronger than in the full sample is one clue that deserves further attention. According to the antecedent hypothesis, excluding study subjects who were previously depressed should weaken the pain-PPD symptoms association, not strengthen it. In reality, all three causal hypotheses probably describe the association between pain and PPD in a Canadian puerperal population to some degree. Fishbain et al. (14) believe that "the scar hypothesis may apply more to patient with major depression, and the consequence hypothesis to pain of the neuropathic type (ex: caesarean section or operative vaginal deliveries)". (14) Further prospective studies are needed to confirm whether or not pain can be placed on a direct pathway to postpartum depression and be considered as one of the causes of PPD.

There were no significant effect modifications or biological interactions found in this study, possibly due to the lack of power required to detect an effect modification or interaction. However, interesting trends were observed. For example, the association between perinatal pain and PPD symptoms appears to be stronger for women who report adequate social support. The protective effect of social support on PPD symptoms is well established. However, evidence suggests that social support may not have the same protective effect on pain, as it could act as a positive re-enforcer of pain behaviours. (29)

To our knowledge, this is the first large-scale study to directly examine the association of perinatal pain with PPD symptoms in Canadian women. The MES was conducted in a nationally representative sample of Canadian women. The results can therefore be generalized to the puerperal population in Canada. Rich social-demographic, clinical, and psychological information collected by the MES allowed a thorough adjustment of potential confounding factors. We have also been able to perform sensitivity analyses. Results from the main analyses, stratified analyses, and sensitivity analyses were consistent and suggest that our study findings are robust.

Our study was probably somewhat affected by misclassification bias. Both perinatal pain and PPD symptoms were subjective measures, and the tool used to classify respondents according to PPD symptom severity, the EPDS, is a screening tool, not a diagnostic tool. Also, it was not possible to find out for each respondent when exactly pain subsided. However, the misclassifications were likely non-differential. This would have biased the results towards the null.

There is also a non-negligible risk that recall bias was introduced in the study as some respondents might have been depressed at the time of interview and their memory and assessment of pain and other symptoms from the previous months might have been distorted. It is highly likely that their recall of pain and other symptoms could differ significantly from the recall of healthy respondents. Differential recall of pain and other symptoms in the postpartum period in turn could have led to reverse causality bias and could offer an alternative interpretation of the association between pain and PPD symptoms in this study. As a result, caution should be applied in the interpretation of these study findings.

Appendix A.        Variable Definition

Category           Variable Name          Definition       Type

SES and            Maternal               Age of           Categorical
demographic        age                    mother
                                          at time of
                                          interview

                   Maternal               Mother's         Categorical
                   education              educational
                                          level

                   Maternal               Mothers          Categorical
                   marital                marital
                   status                 status

                   Household              Household        Categorical
                   annual                 income for the
                   income                 past 12 months

                   Maternal               Region of        Categorical
                   region of              residence of
                   residence              respondents at
                                          time of 2006
                                          census

                   Dwelling               Size of area     Categorical
                   area                   of residence
                                          from the
                                          2006 census

                   Maternal               Whether mother   Binary
                   nativity               is
                   status                 foreign-born
                                          or not

                   Maternal               First Nations,   Binary
                   Aboriginal             Metis or Inuit
                   status

                   Type of                The final        Binary
                   birth                  method of

                   Operative              Use of forceps   Binary
                   delivery--forceps      to aid in
Obstetric                                 delivery
and health
                   Operative              Use of vacuum    Binary
                   delivery--vacuum       to aid in
                                          delivery

                   Operative              A cut to         Binary
                   delivery--episiotomy   enlarge vagina
                                          for delivery

                   Maternal stitches      Stitches to      Binary
                                          repair a tear
                                          or a cut

                   Maternal parity        Number of live   Binary
                                          births

                   Postpartum contact     Whether          Categorical
                   by public              respondents
                   health nurse           were contacted
                                          or not by a
                                          public health
                                          nurse

                   Sex of baby            Sex of baby      Binary

                   Maternal prenatal      Attended         Binary
                   education              prenatal
                                          education

                   Non-medical pain       Use of           Binary
                   relief                 non-medical
                                          pain relief
                                          such as
                                          birthing ball
                                          massage,
                                          positioning,
                                          etc.

                   Medical pain relief    Use of medical   Binary
                                          pain relief
                                          such as
                                          epidural,
                                          Demerol, or
                                           nitrous oxide

                   Postpartum period of   Age of baby at   Binary
                    interview             time of
                                          interview

                   Infant Neonatal        Admission of     Categorical
                   Intensive Care         the baby to
                   Unit (NICU)            NICU
                   admission

                   Maternal previous      Previous         Binary
                   no-live births         pregnancies
                                          not ending in
                                          live births

                   Maternal smoking       Maternal         Binary
                                          smoking

                   Previous               Health           Binary
                   pre-pregnancy health   problems
                   problem                before
                                          pregnancy

                   Maternal new health    New health       Binary
                    problem               problem in
                                          pregnancy

                   Maternal body mass     Pre-pregnancy
                   index                  body mass
                                          index

                   Reaction to            First reaction   Categorical
                   pregnancy              to becoming
                                          pregnant

                   Perceived stress       Self-perceived   Binary
Psychosocial and                          stress during
psychological                             pregnancy

                   Stressful events       Number of        Binary
                                          stressful
                                          events in the
                                          12 months
                                          before birth
                                          of baby

                   Social support         Perceived        Categorical
                                          social support

                   History of             Previous         Binary
                   depression             diagnosis of
                                          depression or
                                          having
                                          been
                                          prescribed
                                          antidepressants

                   Alcohol use            Use of alcohol   Binary
                                          during
                                          pregnancy

                   Drug use               Use of street    Binary
                                          drugs in
                                          pregnancy

                   History of abuse       Experience of    Binary
                                          any type of
                                          violent abuse
                                          in the past 2
                                          years

Appendix B. Tables 1-3

Table 1. Descriptive Statistics and Results From the Confounding
Analyses for the SES and Demographic Variables

                  Outcome: Presence of Problematic Pain

SES and           Total    Pain         Pain    95% CI    PPD
Demographics

Variables         Sample   Prevalence   Crude             Prevalence
                  Size     ([dagger])   OR

Maternal age
(years)

15-19 *           155      87.4%        1.6     1.0-2.7   14.5%

20-24             680      85.7%        1.4     1.1-1.8   8.4%

25-29 (ref)       1693     80.9%                          6.0%

30-34             1962     81.4%        1.0     0.9-1.2   6.4%

35-39             921      81.5%        1.0     0.8-1.3   7.9%

>40 *             203      76.7%        0.8     0.6-1.1   8.7%

Maternal
education

No high school    452      81.9%        1.0     0.8-1.3   13.0%

High school       786      81.5%        1.0     0.8-1.2   8.9%
graduation

Post-secondary    2423     81.6%        1.0     0.8-1.2   6.6%

Bachelors (ref)   1953     81.8%                          5.6%

Maternal marital
status

Married/common    5085     81.5%                          6.5%
law (ref)

Divorced/         102      77.9%        0.8     0.5-1.3   16.3%
widowed *

Single            427      85.5%        1.3     1.0-1.8   11.1%

Household annual
income

< $20,000         503      82.2%        1.0     0.8-1.4   14.1%

$20,000-$39,999   998      83.1%        1.1     0.9-1.4   9.7%

$40,000-$59,999   1088     82.1%        1.0     0.8-1.3   6.3%

$60,000-$79,999   1016     81.7%        1.0     0.8-1.3   5.4%

$80,000-          716      79.2%        0.8     0.7-1.1   5.0%

$99,999 *

> $100,000 (ref)  1034     81.8%                          4.7%

Unknown *         259      80.1%        0.9     0.6-1.3   9.7%

Maternal region
of residence

Atlantic          1016     80.3%        0.8     0.7-1.0   6.0%

Quebec            1035     82.8%        1.0     0.8-1.2   7.5%

Ontario (ref)     1667     82.9%                          7.5%

Prairies          1175     79.7%        0.8     0.7-1.0   6.1%

British Columbia  552      79.3%        0.8     0.6-1.0   6.2%

Territories       169      77.4%        0.7     0.5-0.9   9.9%

Rural dwelling    1255     80.0%        0.9     0.7-1.0   5.8%

Urban dwelling    4359     82.0%                          7.2%
(ref)

Maternal
nativity status

Yes               975      84.2%        1.3     1.0-1.5   11.2%

No (ref)          4639     81.0%                          5.8%

Maternal
Aboriginal
status

Yes *             329      80.0%        0.9     0.7-1.2   10.5%

No (ref)          5285     81.7%                          6.8%

Appendix B.

Table 2. Descriptive Statistics and Results From the Confounding
Analyses for the Obstetric and Health Variables

                       Outcome: Presence of Problematic Pain

Obstetric and Health   Total    Pain         Pain    95%    PPD
Variables              Sample   Prevalence   Crude   CI     Prevalence
                       Size     ([dagger])   OR

Type of birth

Vaginal birth (ref)    4134     81.2%                       7.2%
Caesarean birth        1480     83.0%        1.1     1.0-   6.3%
                                                     1.3

Operative
delivery--Forceps

Yes                    291      87.0%        1.5     1.1-   8.4%
                                                     2.2

No (ref)               5323     81.4%                       6.9%

Operative
delivery--Vacuum

Yes                    490      87.5%        1.6     1.2-   5.4%
                                                     2.2

No (ref)               5124     81.1%                       7.1%

Operative
delivery--Episiotomy

Yes                    900      87.2%        1.6     1.3-   8.3%
                                                     2.0

No (ref)               4714     80.5%                       6.7%

Maternal stitches

Yes                    2973     84.4%        1.5     1.3-   7.1%
                                                     1.7

No (ref)               2641     78.5%                       6.9%

Maternal parity

One (ref)              2550     86.2%                       6.0%

Two                    2067     79.5%        0.6     0.5-   6.9%
                                                     0.7

Three                  693      76.8%        0.5     0.4-   9.2%
                                                     0.7

Four +                 304      70.0%        0.4     0.3-   10.7%
                                                     0.5

Postpartum contact
by public health
nurse

Yes (ref)              5247     81.7%                       6.7%
No                     367      81.0%        1.0     0.7-   10.2%
                                                     1.3

Sex of baby

Male (ref)             2885     81.6%                       7.0%
Female                 2729     81.7%        1.0     0.9-   7.0%
                                                     1.2

Maternal prenatal
education

Yes (ref)              1903     85.5%                       5.6%
No                     3711     79.8%        0.7     0.6-   7.7%
                                                     0.8

Maternal use of
non-medical pain
relief

Yes (ref)              4324     81.4%                       6.7%
No                     1290     82.7%        1.1     0.9-   7.8%
                                                     1.3

Maternal use of
medical pain relief

Yes (ref)              4531     83.5%                       7.2%
No                     1083     74.4%        0.6     0.5-   6.3%
                                                     0.7

Postpartum period of
survey

Early postpartum       1592     81.1%        0.9     0.7-   6.3%
                                                     1.1

Mid postpartum         2750     81.7%        1.0     0.8-   7.2%
                                                     1.2

Late postpartum (ref)  1272     82.4%                       7.5%

Infant neonatal
intensive care unit
admission

Yes                    720      82.3%        1.1     0.8-   8.2%
                                                     1.3

No (ref)               4894     81.6%                       46.5%

Maternal previous
no-live birth

Yes                    1785     80.8%        0.9     0.8-   8.3%
                                                     1.1

No (ref)               3829     82.1%                       6.4%

Maternal smoking

Yes                    1032     82.1%        1.0     0.8-   9.9%
                                                     1.3

No (ref)               4582     81.6%                       6.4%

Maternal
pre-pregnancy health
problems

Yes                    893      81.7%        1.0     0.8-   10.2%
                                                     1.2

No (ref)               4721     81.7%                       6.4%

                       Outcome: Presence of Problematic Pain

Obstetric and Health   Total    Pain         Pain    95%    PPD
Variables              Sample   Prevalence!  Crude   CI     Prevalence
                       Size                  OR

Maternal new health
problems

Yes                    1389     84.4%        1.3     1.1-   9.3%
                                                     1.5

No (ref)               4225     80.8%                       6.3%

Maternal body mass
index

Underweight            274      82.1%        1.0     0.7-   7.5%
                                                     1.3

Normal (ref)           3205     82.4%                       6.6%
Overweight             1287     80.0%        0.9     0.7-   6.8%
                                                     1.0

Obese                  848      81.0%        0.9     0.7-   8.6%
                                                     1.1

                                      Outcome: Postpartum Depression

Obstetric and Health   PPD     95%    Adjusted   95%     Adjusted
Variables              Crude   CI     OR:        CI      OR:
                       OR             Model 1.           Model 2
                                      ([double           ([section])
                                      dagger])

Type of birth

Vaginal birth (ref)
Caesarean birth        0.9     0.7-   0.8        0.5-    0.8
                               1.1               1.3

Operative
delivery--Forceps

Yes                    1.2     0.8-   1.1        0.6-    1.1
                               2.0               2.0

No (ref)

Operative
delivery--Vacuum

Yes                    0.7     0.5-   0.7        0.4-    0.7
                               1.2               1.1

No (ref)

Operative
delivery--Episiotomy

Yes                    1.3     0.9-   1.1        0.8-    1.2
                               1.7               1.7

No (ref)

Maternal stitches

Yes                    1.0     0.8-   1.1        0.8-    1.1
                               1.3               1.6

No (ref)

Maternal parity

One (ref)

Two                    1.2     0.9-   1.2        0.8-    1.2
                               1.5               1.7

Three                  1.6     1.2-   1.3        0.8-    1.3
                               2.2               2.1

Four +                 1.9     1.2-   1.2        0.7-    1.2
                               2.9               2.3

Postpartum contact
by public health
nurse

Yes (ref)
No                     1.6     1.1-   1.5        1.0-    1.5
                               2.3               2.3

Sex of baby

Male (ref)
Female                 1.0     0.8-   1.0        0.8,    1.0
                               1.2               1.3

Maternal prenatal
education

Yes (ref)
No                     1.4     1.1-   1.1        0.8-    1.1
                               1.7               1.5

Maternal use of
non-medical pain
relief

Yes (ref)
No                     1.2     0.9-   1.2        0.9-    1.2
                               1.5               1.8

Maternal use of
medical pain relief

Yes (ref)
No                     0.9     0.7-   0.8        0.6-    0.8
                               1.2               1.1

Postpartum period of
survey

Early postpartum       0.8     0.7-   0.9        0.6-    0.9
                               1.1               1.2

Mid postpartum         1.1     0.9-   1.0        0.7-    1.0
                               1.3               1.4

Late postpartum (ref)

Infant neonatal
intensive care unit
admission

Yes                    1.2     0.9-   1.1        0.7-    1.0
                               1.7               1.5

No (ref)

Maternal previous
no-live birth

Yes                    1.3     1.1-   1.0        0.8-    1.0
                               1.6               1.3

No (ref)

Maternal smoking

Yes                    1.6     1.2-   1.0        0.7-    1.0
                               2.1               1.5

No (ref)

Maternal
pre-pregnancy health
problems

Yes                    1.7     1.3-   1.4        1.0-    1.3
                               2.1               1.9

No (ref)

                                      Outcome: Postpartum Depression

Obstetric and Health   PPD     95% CI Adjusted   95%     Adjusted
Variables              Crude          OR:        CI      OR:
                       OR             Model 1            Model 2
                                      ([double           ([section])
                                      dagger])

Maternal new health
problems

Yes                    1.5     1.2-   1.3        1.0-    1.3
                               1.9               1.7

No (ref)

Maternal body mass
index

Underweight            1.1     0.7-   0.8        0.5-    0.8
                               1.9               1.4

Normal (ref)
Overweight             1.0     0.8-   1.0        0.7-    1.0
                               1.3               1.3

Obese                  1.3     1.0-   1.0        0.7-    1.0
                               1.8               1.4

Obstetric and Health   95%    Adjusted       95%
Variables              CI     OR:            CI
                              Model 3
                              ([parallel])

Type of birth

Vaginal birth (ref)
Caesarean birth        0.5-   0.8            0.5-
                       1.3                   1.2

Operative
delivery--Forceps

Yes                    0.6-   1.1            0.6-
                       1.9                   1.9

No (ref)

Operative
delivery--Vacuum

Yes                    0.4-   0.6            0.4-
                       1.1                   1.1

No (ref)

Operative
delivery--Episiotomy

Yes                    0.8-   1.1            0.8-
                       1.7                   1.6

No (ref)

Maternal stitches

Yes                    0.8-   1.2            0.8-
                       1.6                   1.6

No (ref)

Maternal parity

One (ref)

Two                    0.8-   1.1            0.8-
                       1.7                   1.6

Three                  0.8-   1.3            0.8-
                       2.1                   2.0

Four +                 0.7-   1.2            0.7-
                       2.3                   2.3

Postpartum contact
by public health
nurse

Yes (ref)
No                     0.9-   1.4            0.9-
                       2.3                   2.3

Sex of baby

Male (ref)
Female                 0.8-   1.0            0.8-
                       1.3                   1.3

Maternal prenatal
education

Yes (ref)
No                     0.8-   1.1            0.8-
                       1.5                   1.6

Maternal use of
non-medical pain
relief

Yes (ref)
No                     0.9-   1.2            0.9-
                       1.8                   1.8

Maternal use of
medical pain relief

Yes (ref)
No                     0.6-   0.8            0.6-
                       1.2                   1.2

Postpartum period of
survey

Early postpartum       0.6-   0.9            0.6-
                       1.2                   1.2

Mid postpartum         0.8-   1.0            0.8-
                       1.4                   1.4

Late postpartum (ref)

Infant neonatal
intensive care unit
admission

Yes                    0.7-   1.0            0.7-
                       1.5                   1.5

No (ref)

Maternal previous
no-live birth

Yes                    0.8-   1.1            0.8-
                       1.4                   1.4

No (ref)

Maternal smoking

Yes                    0.7-   1.0            0.7-
                       1.5                   1.5

No (ref)

Maternal
pre-pregnancy health
problems

Yes                    1.0-   1.3            1.0-
                       1.8                   1.8

No (ref)

Obstetric and Health   95%    Adjusted       95%
Variables              CI     OR:            CI
                              Model 3
                              ([parallel])

Maternal new health
problems

Yes                    1.0-   1.3            1.0-
                       1.7                   1.7

No (ref)

Maternal body mass
index

Underweight            0.5-   0.8            0.5-
                       1.4                   1.4

Normal (ref)
Overweight             0.7-   1.0            0.7-
                       1.3                   1.3

Obese                  0.7-   1.0            0.7-
                       1.4                   1.4

* Interpret with caution, 16.6 < CV [less than or equal to] 33.3:
high sampling variability.

([dagger]) All prevalences and odds ratios as well as 95% CI
were obtained using bootstrap weights.

([double dagger]) Model 1: Multivariate logistic regression predicting
PPD with presence of postpartum pain as main exposure.

([section]) Model 2: Multivariate logistic regression predicting PPD
with the duration of pain as main exposure.

([parallel]) Model 3: Multivariate logistic regression predicting PPD
with the number of chronic pains as main exposure.

Appendix B.

Table 3. Descriptive Statistics and Results From the Confounding
Analyses for the Psychosocial and Psychological Variables

                       Outcome: Presence of Problematic Pain

Psychosocial and       Total    Pain         Pain    95%    PPD
Psychological          Sample   Prevalence   Crude   CI     Prevalence
Variables              Size     ([dagger])   OR

Reaction to
pregnancy

Negative               408      82.1%        1.03    0.8-   13.7%
                                                     1.4

Positive (ref)         5206     81.6%                       6.5%

Perceived stress

High                   3203     84.9%        1.6     1.4-   10.0%
                                                     1.9

Low (ref)              2411     77.4%                       3.1%

Stressful events

None (ref)             2170     79.9%                       3.3%

One event              1546     82.3%        1.2     1.0-   6.3%
                                                     1.4

Two events             912      80.7%        1.1     0.9-   7.9%
                                                     1.3

Three events           497      84.6%        1.4     1.1-   13.8%
                                                     1.8

Four events or more    489      87.1%        1.7     1.2-   19.0%
                                                     2.3

Social support

Adequate (ref)         4990     81.5%                       5.8%
Inadequate             624      83.1%        1.1     0.9-   16.1%
                                                     1.4

History of
depression

Yes                    895      84.3%        1.3     1.0-   13.4%
                                                     1.5

No (ref)               4719     81.2%                       5.8%

Alcohol use
(pregnancy)

Yes                    534      83.9%        1.2     0.9-   8.0%
                                                     1.5

No (ref)               5080     81.4%                       6.9%

Drug use (pregnancy)
*

Yes                    51       93.8%        3.4     1.0-   25.0%
                                                     11.6

No (ref)               5563     81.6%                       6.8%

History of abuse

Yes                    674      87.2%        1.6     1.2-   15.3%
                                                     2.0

No (ref)               4940     81.0%                       6.0%

                                      Outcome: Postpartum Depression

Psychosocial and       PPD     95%    Adjusted   95%    Adjusted
Psychological          Crude   CI     OR:        CI     OR:
Variables              OR             Model 1           Model 2
                                      ([double          ([section])
                                      dagger])

Reaction to
pregnancy

Negative               2.3     1.7-   1.3        0.9-   1.2
                               3.1               1.9

Positive (ref)

Perceived stress

High                   3.5     2.6-   2.5        1.8-   2.5
                               4.6               3.4

Low (ref)

Stressful events

None (ref)

One event              2.0     1.4-   1.5        1.1-   1.5
                               2.8               2.2

Two events             2.5     1.7-   1.9        1.3-   1.8
                               3.7               2.8

Three events           4.7     3.2-   2.7        1.8-   2.7
                               7.0               4.3

Four events or more    6.9     4.8-   3.3        2.1-   3.1
                               9.8               5.2

Social support

Adequate (ref)
Inadequate             3.1     2.4-   1.9        1.4-   1.8
                               4.0               2.5

History of
depression

Yes                    2.5     1.9-   2.0        1.5-   2.0
                               3.2               2.7

No (ref)

Alcohol use
(pregnancy)

Yes                    1.2     0.8-   1.2        0.8-   1.2
                               1.7               1.8

No (ref)

Drug use (pregnancy)
*

Yes                    4.5     2.1-   2.1        0.8-   2.1
                               9.7               5.5

No (ref)

History of abuse

Yes                    2.8     2.2-   1.6        1.2-   1.6
                               3.6               2.3

No (ref)

Psychosocial and       95%    Adjusted       95%
Psychological          CI     OR:            CI
Variables                     Model 3
                              ([parallel])

Reaction to
pregnancy

Negative               0.8-   1.2            0.8-
                       1.8                   1.9

Positive (ref)

Perceived stress

High                   1.8-   2.4            1.8-
                       3.4                   3.3

Low (ref)

Stressful events

None (ref)

One event              1.0-   1.5            1.0-
                       2.1                   2.1

Two events             1.2-   1.9            1.2-
                       2.7                   2.8

Three events           1.7-   2.7            1.7-
                       4.1                   4.2

Four events or more    1.4-   3.1            2.0-
                       4.9                   5.0

Social support

Adequate (ref)
Inadequate             1.3-   1.7            1.2-
                       2.4                   2.3

History of
depression

Yes                    1.5-   1.9            1.5-
                       2.6                   2.6

No (ref)

Alcohol use
(pregnancy)

Yes                    0.8-   1.2            0.8-
                       1.8                   1.8

No (ref)

Drug use (pregnancy)
*

Yes                    0.8-   2.2            0.8-
                       5.4                   5.6

No (ref)

History of abuse

Yes                    1.1-   1.6            1.1-
                       2.2                   2.2

No (ref)

* Interpret with caution, 16.6 < CV [less than or equal to]
33.3: high sampling variability.

([dagger]) All prevalences and odds ratios as well as 95% CI
were obtained using bootstrap weights.

([double dagger]) Model 1: Multivariate logistic regression
predicting PPD with presence of postpartum pain as main exposure.

([section]) Model 2: Multivariate logistic regression predicting PPD
with the duration of pain as main exposure.

([parallel]) Model 3: Multivariate logistic regression predicting
PPD with the number of chronic pains as main exposure.

CONCLUSION

In summary, our analysis based on a large national representative sample of postpartum women revealed that problematic perinatal pain was a major risk factor for PPD symptoms. Although postpartum experience of pain is very common, excessive pain should not be dismissed as a normal consequence of childbirth. Women who report considerable amounts of pain postpartum should be systematically screened for PPD symptoms and should be offered the opportunity of pain control measures such as counselling and pain-relieving therapies.

Correspondence: Caroline Gaudet, Centre local de services communautaires Metro (CLSC Metro), 1801 boul. de Maisonneuve Ouest, Montreal, QC H3H 1J9, Tel: 514934-0354, ext. 7256, E-mail: caroline.gaudet1@gmail.com or caroline.gaudet@mcgill.ca

Acknowledgements: At the time of the study, Caroline Gaudet was an MSc (Epidemiology) candidate and a recipient of a Frederick Banting and Charles Best Canada Graduate Scholarships--Master's Award from the Canadian Institutes of Health Research (CIHR). The authors thank the staff at the Carleton, Ottawa, Outaouais Local Research Data Centre (COOL-RDC) for their help in accessing the survey data.

Disclaimers: The present research and analyses are based on data from Statistics Canada and the opinions expressed do not represent the views of Statistics Canada.

Conflict of Interest: None to declare.

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Received: April 29, 2013

Accepted: September 17, 2013

Caroline Gaudet, MSc, OT, [1,2] Shi Wu Wen, MB, PhD, [3,5] Mark C. Walker, MSc, MD, FRCSC [3-5]

Author Affiliations

[1.] School of Physical and Occupational Therapy, McGill University, Montreal, QC

[2.] Centre de sante et de services sociaux de la Montagne, Montreal, QC

[3.] OMNI research group, Ottawa Hospital Research Institute, Ottawa, ON

[4.] Department of Epidemiology and Community Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON

[5.] Department of Obstetrics and Gynecology, Faculty of Medicine, University of Ottawa, Ottawa, ON

Table 1. Maternity Experiences Survey Respondent Characteristics
(n = 5,614)

Main Exposure         n       %        Obstetric and Health
Variables                              Variables

1) Presence of                         Caesarean birth
problematic
perinatal pain in     4553    81.7%    Operative
the first three                        delivery--Forceps
months postpartum

                                       Operative
                                       delivery--Vacuum

2) Duration of                         Operative
problematic                            delivery--Vacuum
perinatal pain

None *                1061    18.3%    Operative
(reference)                            delivery--Episiotomy

Acute pain only       3085    54.6%    Maternal stithces

Chronic pain          1468    27.1%    Maternal parity

3) Number of types                     One (reference)
of perinatal pains
at the time of                         Two
interview

None (reference)      4146    72.9%    Three

One                   1193    21.8%    Four +

Two                   241     4.6%     No postpartum contact
                                       by public health
                                       nurse

Three or more         34      0.6%*    Female baby

Socio-demographic     n       %        No maternal prenatal
variables                              education

Maternal age                           No maternal use of
(years)                                non-medical pain
                                       relief

15-19 *               155     1.8%     No maternal use of
                                       medical pain relief

20-24                 680     11.2%    Postpartum period of
                                       interview

25-29 (reference)     1693    31.0%    Early postpartum

30-34                 1962    35.3%    Mid postpartum

35-39                 921     16.8%    Late postpartum
                                       (reference)

> 40 *                203     3.8%     Infant neonatal
                                       intensive care unit
                                       admission

Maternal education                     Maternal previous
                                       no-live birth

No high school        452     7.2%     Maternal smoking

High school           786     13.3%    Maternal pre-pregnancy
graduation                             health problems

Post-secondary        2423    43.4%    Maternal new health
                                       problems

Bachelors             1953    36.2%    Maternal body mass
(reference)                            index

Maternal marital                       Underweight
status

Married/common law    5085    92.2%    Normal (reference)
(reference)

Divorced/widowed *    102     1.8%     Overweight

Single                427     6.0%     Obese

Household annual
income

< $20,000             503     8.0%     Psychosocial and
                                       Psychological
                                       Variables

$20,000-$39,999       998     16.6%    Negative reaction to
                                       pregnancy

$40,000-$59,999       1088    19.2%    High perceived stress

$60,000-$79,999       1016    18.4%    Stressful events

$80,000-$99,999 *     716     13.4%    None (reference)

> $100,000            1034    19.8%    One event
(reference)

Unknown *             259     4.7%     Two events

Maternal region of                     Three events
residence

Atlantic              1016    6.2%     Four events or more

Quebec                1035    22.6%    Inadequate social
                                       support
Ontario (reference)   1667    40.0%    History of depression

Prairies              1175    19.1%    Alcohol use
                                       (pregnancy)

British Columbia      552     11.7%    Drug use (pregnancy) *

Territories           169     0.4%     History of abuse

Rural dwelling        1255    18.2%

Maternal nativity     975     22.2%
status
(foreign-born)

Maternal Aboriginal   329     4.1%
status

Main Exposure         Total     Proportion
Variables             Sample
                      Size

1) Presence of        1480      26.4%
problematic
perinatal pain in     291       5.3%
the first three
months postpartum

2) Duration of        490       9.0%
problematic
perinatal pain

None *                900       17.0%
(reference)

Acute pain only       2973      53.6%

Chronic pain

3) Number of types    2550      45.3%
of perinatal pains
at the time of        2067      37.1%
interview

None (reference)      693       12.3%

One                   304       5.2%

Two                   367       6.9%

Three or more         2729      48.7%

Socio-demographic     3711      67.3%
variables

Maternal age          1290      23.3%
(years)

15-19 *               1083      19.9%

20-24

25-29 (reference)     1592      28.9%

30-34                 2750      50.5%

35-39                 1272      20.7%

> 40 *                720       12.8%

Maternal education    1785      32.3%

No high school        1032      16.1%

High school           893       15.2%
graduation

Post-secondary        1389      24.4%

Bachelors
(reference)

Maternal marital      274       5.3%
status

Married/common law    3205      58.9%
(reference)

Divorced/widowed *    1287      21.9%

Single                848       13.9%

Household annual
income

< $20,000             n         %

$20,000-$39,999       408       6.6%

$40,000-$59,999       3203      56.9%

$60,000-$79,999

$80,000-$99,999 *     2170      39.6%

> $100,000            1546      28.4%
(reference)

Unknown *             912       15.7%

Maternal region of    497       8.6%
residence

Atlantic              489       7.7%

Quebec                624       12.0%

Ontario (reference)   895       15.4%

Prairies              534       10.7%

British Columbia      51        0.9%

Territories           674       10.8%

Rural dwelling

Maternal nativity
status
(foreign-born)

Maternal Aboriginal
status

* Interpret with caution, 16.6 < CV < 33.3: high sampling variability.

Table 2. Descriptive Statistics As Well As Crude and Adjusted Odds
Ratios (OR) and 95% Confidence Intervals for the Associations Between
the Main Pain Exposures of Interest and Postpartum Depression Symptoms
in Canadian Women (n = 5,614)

Exposure       n      PPD          Crude    Adjusted       Adjusted
                      Symptoms     OR       OR:            OR:
                      Prevalence            SES            Obstetric
                      ([dagger])            /demographic   /health

Presence
of
problematic
perinatal
pain

No (ref)       1061   3.7%
Yes            4553   7.7%         2.2      2.1            2.2
                                   (1.5-    (1.5-3.1)      (1.6-3.2)
                                   3.1)

Duration of
problematic
perinatal
pain

None (ref) *   1061   3.7%

Acute only     3085   5.3%         1.5      1.7            1.5
                                            (1.0-2.2)      (1.0-2.2)

Chronic        1468   12.7%        3.8      3.4            3.8
                                   (2.6-    (2.3-5.1)      (2.6-5.7)
                                   5.6)

Number of
types of
perinatal
pains at the
time of
interview

None           4146   4.9%

One            1193   10.0%        2.2      1.55-2.58      2.1
                                   (1.7-                   (1.6-2.7)
                                   2.8)

Two            241    22.6%        5.7      4.7            5.7
                                   (4.0-    (3.3-6.8)      (3.9-8.2)
                                   8.1)

Three +        34     33.5%        9.8      7.1            8.7
                                   (4.6-    (3.1-16.0)     (3.6-
                                   21.1)                   21.0)

Exposure       n      Adjusted         Adjusted    Adjusted
                      OR:              OR:         OR:
                      Psychological    SES/dem.,   SES/dem.,
                      /psychosocial    obstetric   psychological
                                       /health     /psychosocial
Presence
of
problematic
perinatal
pain

No (ref)       1061
Yes            4553   1.8 (1.3-2.7)    2.1         1.7 (1.2-2.5)
                                       (1.4-
                                       3.1)

Duration of
problematic
perinatal
pain

None (ref) *   1061

Acute only     3085   1.3 (0.9-1.9)    1.5         1.3 (0.9-1.9)
                                       (1.0-
                                       2.2)

Chronic        1468   2.5 (1.6-3.7)    2.4         2.5 (1.6-3.7)
                                       (2.3-
                                       5.0)

Number of
types of
perinatal
pains at the
time of
interview

None           4146

One            1193   1.7 (1.3-2.3)    1.9         1.7 (1.3-2.2)
                                       (1.5-
                                       2.5)

Two            241    3.7 (2.5-5.5)    4.7         3.1 (2.1-4.7)
                                       (3.2-
                                       6.9)

Three +        34     5.9 (1.9-17.9)   6.5         4.4
                                       (2.5-       (0.9-21.0)
                                       16.7)

Exposure       n      Adjusted         Final Model:   Final Model:
                      OR:              OR Adjusted    Multiply
                      Obst./health,    for All        Imputed
                      psychological    Variables      Dataset
                      /psychosocial
Presence
of
problematic
perinatal
pain

No (ref)       1061
Yes            4553   1.8 (1.3-2.6)    1.7            1.8
                                       (1.2-2.5)      (1.4-2.1)

Duration of
problematic
perinatal
pain

None (ref) *   1061

Acute only     3085   1.3 (0.9-2.0)    1.3            1.4
                                       (0.9-1.9)      (0.6-2.2)

Chronic        1468   2.7 (1.8-4.0)    2.4            2.4
                                       (1.6-3.6)      (1.6-3.2)

Number of
types of
perinatal
pains at the
time of
interview

None           4146

One            1193   1.7 (1.3-2.3)    1.7            1.6
                                       (1.3-2.2)      (1.4-1.9)

Two            241    3.8 (2.6-5.7)    3.2            2.6
                                       (2.1-4.9)      (2.2- 3.0)

Three +        34     5.5              4.2            4.1
                      (1.4-22.7)       (0.7-25.0)     (3.0-5.1)

Exposure       n      Final Model:
                      Never
                      Previously
                      Depressed
                      Subsample
Presence
of
problematic
perinatal
pain

No (ref)       1061
Yes            4553   2
                      (1.2-3.2)

Duration of
problematic
perinatal
pain

None (ref) *   1061

Acute only     3085   1.5
                      (0.9-2.5)

Chronic        1468   2.8
                      (1.7-4.7)

Number of
types of
perinatal
pains at the
time of
interview

None           4146

One            1193   1.7
                      (1.2-2.3)

Two            241    3.4
                      (2.1-5.7)

Three +        34     5.1
                      (0.0-8.5)

* Interpret with caution, 16.6 < CV [less than or equal to]
33.3: high sampling variability.

([dagger]) All prevalences and odds ratios as well as 95% CI
were obtained using bootstrap weights.

Table 3. Investigation of the Modification Effect of Selected Variables
on the Associations Between the Main Exposures and Postpartum
Depression Symptoms (n = 5,614)

Variables         n       Presence of Problematic
                          Perinatal Pain in the
                          First Three Variables
                          Months Postpartum

                                        Acute Pain Only

                          Crude OR      Adjusted OR   Crude OR

Maternal
nativity status

Foreign-born      975     4.0           3.8           2.6
                          (1.3-12.2)    (1.0-13.8)    (0.8-8.1)

Canadian-born     4639    1.72          1.3           1.2
                          (1.2-2.6)     (0.8-1.9)     (0.8-1.8)

Type of birth

Caesarean         1480    2.9           2.4           1.8
delivery                  (1.0-7.8)     (0.7-7.4)     (0.6-5.1)

Vaginal           4134    2.1           1.6           1.4
delivery                  (1.4-3.1)     (1.0-2.4)     (0.9-2.1)

Sex of baby

Female            2729    2.9           2.4           1.9
                          (1.6-5.4)     (1.3-4.7)     (1.0-3.5)

Male              2885    1.7           1.3           1.2
                          (1.1-2.8)     (0.8-2.3)     (0.7-2.0)

Non-medical
pain relief

Use               4324    1.9           1.5           1.4
                          (1.3-2.9)     (1.0-2.3)     (0.9-2.1)

No use            1290    3.4           2.9           1.9
                          (1.1-10.7)    (0.7-10.9)    (0.6-6.3)

Medical pain
relief

Use               4531    1.9           1.6           1.3
                          (1.3-2.8)     (1.0-2.4)     (0.9-2.0)

No use            1083    3.7           2.3           2.0
                          (1.4-10.1)    (0.6-9.3)     (0.7-5.7)

Maternal
smoking

Smoker            1032    1.1           0.7              0.7
                          (0.6-2.0)     0.3-1.7)      (0.3-1.3)

Non-smoker        4582    3.0           2.3           2.0
                          (1.9-4.6)     (1.4-3.8)     (1.2-3.2)

Maternal body
mass index

Underweight to    3479    1.7           1.2           1.1
normal                    (1.1-2.6)     (0.8-2.0)     (0.7-1.7)

Obese to          2135    3.8           3.2           2.6
overweight                (1.9-7.6)     (1.5-6.7)     (1.3-5.3)

Social support

Adequate          4990    2.4           1.8           1.7
                          (1.5-3.7)     (1.1-2.9)     (1.1-2.7)

Inadequate        624     1.7           1.5           1.0
                          (0.9-3.4)     (0.6-3.9)     (0.5-2.2)

Variables         n       Duration of Problematic
                          Perinatal Pain

                                         Chronic Pain

                          Adjusted OR    Crude OR     Adjusted OR

Maternal
nativity status

Foreign-born      975     2.6            6.3          5.5
                          (0.7-9.6)      (2.0-19.5)   (1.4-21.0)

Canadian-born     4639    1.0            3.0          1.8
                          (0.6-1.6)      (2.0-4.5)    (1.1-2.7)

Type of birth

Caesarean         1480    1.7            4.5          3.2
delivery                  (0.5-5.6)      (1.6-12.9)   (1.0-10.1)

Vaginal           4134    1.2            3.7          2.3
delivery                  (0.8-1.9)      (2.4-5.7)    (1.5-3.7))

Sex of baby

Female            2729    1.8            5.4          3.6
                          (0.9-3.5)      (2.9-10.0)   (1.8-7.2)

Male              2885    1.0            2.9          1.8
                          (0.6-1.8)      (1.7-4.7)    (1.0-3.2)

Non-medical
pain relief

Use               4324    1.2            3.3          2.1
                          (0.8-1.9)      (2.1-5.0)    (1.3-3.3)

No use            1290    1.8            6.1          4.6
                          (0.4-7.1)      (1.9-19.5)   (1.2-18.1)

Medical pain
relief

Use               4531    1.3            3.0          2.1
                          (0.8-2.0)      (2.0-4.6)    (1.3-3.3)

No use            1083    1.6            9.0          4.8
                          (0.4-6.8)      (3.2-25.2)   (1.0-22.6)

Maternal
smoking

Smoker            1032    0.5            1.8          1.1
                          (0.2-1.3)      (0.9-3.6)    (0.4-2.8)

Non-smoker        4582    1.8            5.1          3.3
                          (1.1-2.9)      (3.2-8.2)    (2.0-5.6)

Maternal body
mass index

Underweight to    3479    0.9            2.9          1.8
normal                    (0.6-1.5)      (1.8-4.7)    (1.1-3.1)

Obese to          2135    2.5            6.4          4.5
overweight                (1.1-5.3)      (3.1-12.9)   (2.1-9.8)

Social support

Adequate          4990    1.4            3.9          2.5
                          (0.9-2.3)      (2.5-6.3)    (1.6-4.2)

Inadequate        624     0.9            2.7          2.2
                          (0.3-2.7)      (1.3-5.5)    (0.8-6.3)

Variables         n       Number of Sites of Problematic Perinatal
                          Pain at the Time of Interview

                          One Site of Pain           Two + Sites of
                                                     Pain

                          Crude OR     Adjusted OR   Crude OR

Maternal
nativity status

Foreign-born      975     2.3          2.22          4.6
                          (1.5-3.7)    (1.2-4.0)     (2.7-8.1)

Canadian-born     4639    2.0          1.4           6.3
                          (1.5-2.7)    (1.0-1.9)     (4.3-9.2)

Type of birth

Caesarean         1480    1.7          1.5           7.0
delivery                  (1.0-2.3)    (0.8-2.8)     (3.9-12.7)

Vaginal           4134    2.4          1.8           6.0
delivery                  (1.8-3.1)    (1.3-2.4)     (4.0-8.9)

Sex of baby

Female            2729    2.6          1.9           6.5
                          (1.8-3.6)    (1.3-2.9)     (4.1-10.3)

Male              2885    1.8          1.4           5.8
                          (1.3-2.6)    (0.9-2.1)     (3.7-9.0)

Non-medical
pain relief

Use               4324    2.1          1.6           5.4
                          (1.5-2.7)    (1.1-2.2)     (3.6-7.9)

No use            1290    2.5          2.1           8.1
                          (1.5-4.2)    (1.1-4.1)     (4.4-14.7)

Medical pain
relief

Use               4531    1.8          1.4           5.6
                          (1.3-2.4)    (1.0-1.9)     (4.0-7.9)

No use            1083    4.8          3.1           9.1
                          (2.7-8.5)    (1.1-8.4)     (3.5-24.1)

Maternal
smoking

Smoker            1032    1.6          1.2           7.1
                          (0.9-2.8)    (0.5-2.6)     (3.7-13.7)

Non-smoker        4582    2.3          1.8           5.9
                          (1.8-3.1)    (1.3-2.5)     (4.0-8.9)

Maternal body
mass index

Underweight to    3479    2.1          1.7           5.8
normal                    (1.5-2.9)    (1.1-2.4)     (3.8-8.7)

Obese to          2135    2.2          1.7           6.8
overweight                (1.5-3.3)    (1.1-2.8)     (4.0-11.5)

Social support

Adequate          4990    2.0          1.5           6.3
                          (1.4-2.6)    (1.1-2.0)     (4.4-9.2)

Inadequate        624     2.3          2.3           3.4
                          (1.4-3.8)    (1.1-4.9)     (1.8-6.3)

Variables         n

                          Adjusted OR

Maternal
nativity status

Foreign-born      975     3.5
                          (1.5-8.1)

Canadian-born     4639    3.8
                          (2.3-6.1)

Type of birth

Caesarean         1480    4.3
delivery                  (1.8-10.4)

Vaginal           4134    3.2
delivery                  (1.9-5.3)

Sex of baby

Female            2729    3.8
                          (2.1-6.8)

Male              2885    3.4
                          (1.9-6.2)

Non-medical
pain relief

Use               4324    3.0
                          (1.8-4.8)

No use            1290    7.3
                          (2.6-20.2)

Medical pain
relief

Use               4531    3.2
                          (2.1-4.9)

No use            1083    4.5
                          (0.8-26.7)

Maternal
smoking

Smoker            1032    5.6
                          (1.8-17.6)

Non-smoker        4582    3.3
                          (2.0-5.3)

Maternal body
mass index

Underweight to    3479    3.3
normal                    (1.9-5.6)

Obese to          2135    4.7
overweight                (2.3-9.5)

Social support

Adequate          4990    4.2
                          (2.7-6.6)

Inadequate        624     2.3
                          (0.7-7.1)