Although there was no statistically significant intervention effect on weight change at any time point,17
there was broad variability in postpartum weight change in this sample of overweight and obese women. Relative to weight at 6 weeks after delivery, mean weight change at each time point was within 0.5–3
kg but ranged from a 21.5
kg loss to a 24.5
kg gain by 24 months postpartum. This pattern and range of postpartum weight change are consistent with other observational studies of postpartum weight retention.1,2,14,15,28,29
Although mean weight retention was modest, 29% of the women in our sample retained ≥5
kg at 24 months postpartum. On average, the women in our study did not return to their prepregnancy weights, and most of their postpartum weight loss occurred within 6 weeks of delivery ().
Weight retained postpartum was positively associated with baseline weight and negatively associated with gestational weight gain at all time points in both the covariate-adjusted and unadjusted analyses. Maternal age and race were associated with weight change at each time point in the unadjusted analyses, but these effects were mitigated in the covariate-adjusted analysis. The effect of living with a partner remained significant in the covariate-adjusted model (at the 18 and 24 month points). The association with marital status has been found elsewhere16
and suggests that single women are at higher risk for long-term pregnancy-related weight retention.
Our study measures weight change beginning at 6 weeks postpartum. A significant part of weight change up to this point represents a natural return to prepregnancy physical status, that is, a loss of retained fluid and other products of pregnancy, whereas weight change after this point is more likely to represent change in accumulated fat stores. In our sample, much of the observed weight loss occurred before 6 weeks postpartum, and for each additional kilogram of weight gained during pregnancy, <0.2
kg was lost from 6 weeks to 24 months postpartum. Further, it is notable that the more obese women were at 6 weeks, the less weight they lost by 24 months; in fact, obese women in classes II and III were likely to gain weight in this period (). Our data suggest that for obese women, pregnancy and the postpartum period compound their obesity problem. This is consistent with the findings of Gunderson et al.,7
who showed that overweight and obese women experienced similar weight loss to normal weight women at 6 weeks postpartum but did not continue to lose and even gained weight in the late (median 2 years) postpartum period. They concluded that these later changes in weight explained heavier women's greater postpartum weight retention.
Although our intervention had limited effect on potentially modifiable behavioral risk factors including diet and physical activity,17
these factors were associated with postpartum weight change. Although an early study by Boardley et al.5
found no such associations, more recent studies support the conclusion that modifiable risk factors do contribute to postpartum weight change. In a study of 540 women, Olson et al.14
found that women who reported exercising often (as compared to never, p
=0.03) and eating a lot less over the previous 6 months (as opposed to no change, p
=0.008) retained significantly less weight at 12 months postpartum. Among 902 women enrolled in the longitudinal Project Viva, Oken et al.15
found that several behaviors reported at 6 months were independently associated with weight retention at 12 months postpartum. Women who watched less than 2 hours of television daily, walked at least 30 minutes, and consumed trans fats below the median had an odds ratio (OR) of 0.23 (95% confidence interval [CI] 0.08-0.66) of retaining ≥5
In our study, both a low junk food score (minimal fast food and soda) and a high healthy food score (high fruit, vegetable, and milk intake) affected postpartum weight loss, although limiting junk food appeared to have a more sizable effect than increasing fruit and vegetables.
Schauberger et al.30
followed a cohort of women to a mean of 8.5 years postpartum. Although they found no effect of physical activity or breastfeeding on weight change at 6 months postpartum in this cohort, both behaviors were associated with reduced weight retention at long-term follow-up.31
Linné et al.32
recontacted their sample 15 years postpartum and did not find an effect of diet or physical activity but did find that breastfeeding after the index pregnancy was associated with reduced weight retention at long-term follow-up. Although there is a substantial effect of breastfeeding in the covariate-unadjusted analysis, this is mitigated in the covariate-adjusted analysis. This is a common finding; the effect of breastfeeding is in general found to be positive but small and easily confounded with other variables, including caloric intake.33–35
Hormonal contraception was associated with greater weight loss in unadjusted analyses at 24 months, but this relationship was only borderline significant (p
=0.06) in the adjusted analysis. Although data regarding the effects of hormonal contraception on weight have varied, Berenson and Rahman36
recently followed a cohort of women using oral contraceptives, depot medroxyprogesterone acetate (DMPA), or nonhormonal methods for up to 3 years. Women using DMPA gained more weight compared to women in the other two groups, and women using oral contraceptives actually lost weight at 12 and 24 months while those using nonhormonal methods gained weight at each time point. The potential benefit of hormonal contraception on weight loss warrants further investigation.
Study strengths include the relatively large sample, good representation of both white and African American women, a long (24 month) follow-up period, and good follow-up rates. Furthermore, the study had standardized, objective measurements of weight (at four times points) and height as well as information on behavioral risk factors, which many observational studies do not.13–15
This study did not collect gestational age, which is a limitation, as we could not adjust gestational weight gain calculations for gestational age.
The perinatal period is one of substantial weight change and retention for women of all weights, but particularly for overweight and obese women. Furthermore, postpartum weight change is associated with behavioral risk factors, such as diet and physical activity, that are modifiable and, therefore, suitable targets for behavioral intervention. Our intervention showed a modest, nonsignificant effect on weight by 12 months, which was not sustained by 24 months. The intervention was relatively elaborate for a public health strategy (in contrast to a clinical strategy), and most participants found it difficult to engage with the intervention in the first year postpartum. Those who did engage in the program, however, lost more weight than those who did not.17
The risk factors associated with this weight gain are to a large extent the same factors that make it more difficult to engage in a formal intervention postpartum, namely, being single or having less education (suggesting less support and fewer financial resources). Our results emphasize the importance of this period in obese women's lives for additional weight gain and the importance of weight control interventions in the postpartum period. Based on the experience with AMP, however, we believe that community-based interventions delivered outside the home are unlikely to impact postpartum weight loss, and more accessible programs delivered in the home via telephone, mail, or internet/e-mail may be more feasible for postpartum women and, therefore, more successful.17