摘要：Objectives . We examined the association between breastfeeding duration and maternal smoking before, during, and after pregnancy. Methods. Data from the 2000–2001 Oregon Pregnancy Risk Assessment Monitoring System were used. Early weaning was defined as not breastfeeding at 10 weeks postpartum. Results. At 10 weeks after pregnancy, 25.7% of mothers who initiated breastfeeding no longer breastfed. After controlling for confounders, quitters (mothers who quit smoking during pregnancy and maintained quit status after pregnancy) and postpartum relapsers (mothers who quit smoking during pregnancy and resumed smoking after delivery) did not have significantly higher risk for early weaning than nonsmokers. However, persistent smokers (mothers who smoked before, during, and after pregnancy) were 2.18 times more likely not to breastfeed at 10 weeks (95% confidence interval=1.52, 2.97). Women who smoked10 or more cigarettes per day postpartum (i.e., heavy postpartum relapsers and heavy persistent smokers) were 2.3–2.4 times more likely to wean their infants before 10 weeks than were nonsmokers. Conclusions. Maternal smoking is associated with early weaning. Stopping smoking during pregnancy and decreasing the number of cigarettes smoked postpartum may increase breastfeeding duration. Breastfeeding is an important contributor to overall infant health, because human breast milk represents the most complete form of nutrition for infants. The American Academy of Pediatrics recommends that infants be exclusively breastfed for approximately the first 6 months of life. 1 One of the United States’ national health goals for 2010 is that at least 75% of new mothers will initiate breastfeeding, at least 50% will continue to breastfeed their infants to 6 months, and 25% will continue to breastfeed their infants at 1 year. 2 In 2002, 71.4% of postpartum women in the United States initially breastfed their infants; 35.1% were still breastfeeding to some extent at 6 months. 3 To achieve the national goal for duration of breastfeeding by 2010, we must further study the factors affecting breastfeeding duration. Maternal smoking is an important factor in early termination of breastfeeding. Many studies have found that mothers who smoke are less likely to initiate breastfeeding 4 – 6 and breastfeed for a shorter time than nonsmokers. 4 – 13 Smoking status, however, has been defined differently across studies: some studies have evaluated smoking status during pregnancy 5 , 11 , 12 or during the postpartum period, 5 , 9 , 13 whereas many other studies have not defined a time frame for smoking status. 6 – 8 , 10 To our knowledge, no breastfeeding study has ever considered the changes in smoking patterns before, during, and after pregnancy. We know, however, that many mothers stop smoking during pregnancy to protect their fetuses, and that most resume after delivery. 14 , 15 The duration of breastfeeding may differ between mothers who have never smoked, quitters, postpartum relapsers, and persistent smokers. A thorough understanding of how the mother’s smoking status around the time of pregnancy is associated with duration of breastfeeding is crucial to the design of programs that encourage smoking cessation as well as programs that promote breastfeeding. Existing studies are also hampered by small sample size and their failure to account for multiple confounding factors. 4 Restricted by the information available for analysis, many studies tend to dichotomize smoking status (i.e., smokers vs nonsmokers), 6 – 8 , 10 , 11 , 13 even though studies have found differences in breastfeeding duration between light and heavy smokers. 5 , 9 , 12 , 16 In summary, a need has emerged to reevaluate the association between maternal perinatal smoking and the duration of breastfeeding using a population-based sample, controlling for multiple confounding factors, and taking into account the changing pattern of smoking status during the perinatal period as well as the dose–response effect of smoking intensity. We examined 2 main research questions: (1) how do patterns of maternal smoking around the time of pregnancy relate to the duration of breastfeeding; and (2) is the association between maternal smoking and breastfeeding duration modified by the intensity of postpartum smoking?
