Weight trajectories across reproductive years up risk of adverse pregnancy outcomes

Weight gains prior to and between pregnancies appear to increase the risk of adverse pregnancy outcomes (APOs), reports a study. A longer period of weight gain shows the most robust association with an increased risk of APOs.

A total of 16,241 women, with 25,386 singleton pregnancies, participated in the prospective cohort of the Nurses’ Health Study II. The authors assessed weight at 18 years, current weight, and height at baseline (1989) and updated data on weight biennially. Pregnancy history was self-reported in 2009.

A composite of hypertensive disorders of pregnancy (HDP), gestational diabetes (GDM), preterm birth, and stillbirth served as the primary outcome, while individual APOs were secondary. The authors then estimated the associations of weight change with APOs using log-binomial regression, adjusted for demographic, lifestyle, reproductive factors, and baseline BMI.

Women had a mean age of 33.7 years at first in-study pregnancy. The mean time from age 18 years to pregnancy was 16.3 years, baseline to pregnancy 6.1 years, and between pregnancies 2.9 years, with weight changes of 6.4, 3.1, and 2.3 kg, respectively. A total of 4,628 (18.2 percent) pregnancies were complicated by at least one APO.

Absolute weight change since age 18 years had the strongest association with APOs. Women who gained >2 kg had a higher risk of APO (2.1‒9.9 kg: relative risk [RR], 1.12, 95 percent confidence interval [CI], 1.02‒1.23; 10.0‒14.9 kg: RR, 1.43, 95 percent CI, 1.29‒1.60; ≥15 kg: RR, 1.87, 95 percent CI, 1.69‒2.08), driven mainly by HDP and GDM, than those whose weight remained stable.

“The associations of per 1 kg weight gain before and between pregnancies with HDP were nearly identical,” the authors said.