摘要：Objectives. We investigated the relationship between childbirth and 5-year incidence of obesity. Methods. We performed a prospective analysis of data on 2923 nonobese, nonpregnant women aged 14 to 22 years from the 1979 National Longitudinal Survey of Youth Cohort, which was followed from 1980 to 1990. We used multivariable logistic regression analyses to determine the adjusted relative risk of obesity for mothers 5 years after childbirth compared with women who did not have children. Results. The 5-year incidence of obesity was 11.3 per 100 parous women, compared with 4.5 per 100 nulliparous women (relative risk [RR] = 3.5; 95% confidence interval [CI] = 2.4, 4.9; P < .001). The 5-year incidence of obesity was 8.6 for primiparous women (RR = 2.8; 95% CI = 1.5, 5.0) and 12.2 for multiparous women (RR = 3.8; 95% CI = 2.6, 5.6). Among parous women, White women had the lowest obesity incidence (9.1 per 100 vs 15.1 per 100 for African Americans and 12.5 per 100 for Hispanics). Conclusions. Parous women have a higher incidence of obesity than do nulliparous women, and minority women have a higher incidence of parity-related obesity than do White women. Thus, efforts to reduce obesity should target postpartum women and minority women who give birth. Women in the United States are disproportionately overweight, particularly minority and socioeconomically disadvantaged women. 1 , 2 Approximately two thirds of adult women are overweight, and of this group, one third are obese. 1 Among racial/ethnic groups, African American and Hispanic women have the highest prevalences of obesity, at 50% and 40%, respectively. 1 Women who are socioeconomically disadvantaged have higher obesity rates than do women of higher socioeconomic standing. 3 In addition, emerging evidence links perinatal factors such as parity (number of births) to obesity in later life, 4 – 9 although researchers investigating the relationship between parity and major weight gain or obesity have found mixed results. 7 , 10 – 17 Several studies have reported that multiparous women (those who have had 2 or more live births) were more likely to be overweight than were nulliparous women (those who have never had a live birth). 10 – 13 , 15 Another study found that primiparous women (those who have had at least 1 live birth) were more likely to be overweight and to have major long-term weight gain than were multiparous and nulliparous women. 17 Other studies have found little or no relationship between parity and weight gain or obesity. 7 , 12 , 14 , 16 The inconsistencies in these findings may stem from differences in definitions of the main outcomes, the use of cross-sectional study designs versus prospective designs, or the exclusion of prevalent cases of obesity at baseline. The majority of these studies focused on the outcomes of mean body mass index (BMI), mean weight gain, weight change, major weight gain, or prevalence of obesity, but not on the incidence of parity-related obesity. Additionally, these studies did not establish that births occurred before the outcome measured. 10 , 12 , 13 , 16 Nor have these studies investigated whether racial/ethnic or socioeconomic differences exist in the incidence of parity-related obesity. Thus, we used prospective data to determine the 5-year incidence of parity-related obesity among our sample and to investigate whether this incidence varied by race/ethnicity or socioeconomic status.
