Timing and Amount of Gestational Weight Gain in Association with Adverse Birth Outcomes

Background: Most existing research on gestational weight gain and pregnancy outcomes has not accounted for timing of weight gain. The area under the weight gain curve (AUC) provides a single measure that incorporates both timing of weight gain and total amount gained. This study evaluated predictors and outcomes associated with second- and third-trimester weight gain AUC from the second and third trimester using time-to-event analysis to account for the correlation between gestational weight gain and gestational duration.

Methods: Our prospective cohort study used data from the LifeCodes study at Brigham and Women's Hospital. Maternal weights were available from all prenatal and study visits. We used log-Poisson models with empirical variance estimation to identify predictors of total AUC from 14 weeks to delivery and Cox proportional hazards models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for the association between AUC quintile and adverse pregnancy outcomes.

Results: Compared to the middle quintile, the highest quintile of accumulated pound-days was associated with a decreased hazard of spontaneous preterm birth among multigravid women (HR = 0.44; 95% CI = 0.23, 0.84), a decreased hazard of small-for-gestational-age births (HR = 0.65; 95% CI = 0.45, 0.92) overall and an increased hazard of large-for-gestational-age births among normal and underweight women (HR = 3.21; 95% CI = 1.50, 6.89) CONCLUSIONS:: In our study, a pattern of gestational weight gain characterized by more rapid gains earlier in pregnancy was associated with improved pregnancy outcomes in some subgroups of pregnant women.