Postpartum weight retention in relation to gestational weight gain and pre-pregnancy body mass index: a prospective cohort study in Vietnam

Background: The prevalence of maternal overweight and obesity is increasing in Asia. This study prospectively investigated the association between pre-pregnancy body mass index (BMI), gestational weight gain (GWG) and 12-month postpartum weight retention (PPWR) in a large cohort of Vietnamese mothers.

Methods: Of the 2030 pregnant women recruited from three cities in Vietnam at 24-28 weeks of gestation, a total of 1666 mothers were followed up for 12 months after delivery and available for analysis. The outcome variable PPWR was determined by subtracting the pre-pregnancy weight from the 12-month postpartum measured weight, while GWG and pre-pregnancy BMI were classified according to the Institute of Medicine and WHO criteria for adults, respectively. Linear regression models were used to ascertain the association between pre-pregnancy BMI, GWG and PPWR accounting for the effects of plausible confounding factors.

Results: Both pre-pregnancy BMI and GWG were significantly associated with PPWR (P<0.001). The adjusted mean weight retention in underweight women before pregnancy (3.71kg, 95% confidence interval (CI) 3.37-4.05) was significantly higher than that in those with normal pre-pregnancy weight (2.34kg, 95% CI 2.13-2.54). Women with excessive GWG retained significantly more weight (5.07kg, 95% CI 4.63-5.50) on average at 12 months, when compared to mothers with adequate GWG (2.92kg, 95% CI 2.67-3.17).

Conclusions: Being underweight before pregnancy and excessive GWG contribute to greater weight retention twelve months after giving birth. Interventions to prevent postpartum maternal obesity should target at risk women at the first antenatal visit and control their weight gain during the course of pregnancy.