Second Trimester Insulin Resistance, Early Pregnancy Body Mass Index and Gestational Weight Gain

Objectives Because prior work suggests an association between high insulin concentrations in early pregnancy and excess gestational weight gain, we examined such associations in a prospective cohort. Methods Multivariate regression analysis of early pregnancy insulin homeostasis and gestational weight gain among 434 women enrolled in the MGH Obstetrical Maternal Study. Results We found that the association between insulin quartile and gestational weight gain varied depending on maternal body mass index (BMI) in early pregnancy (P for interaction <0.0001). Among women with a BMI of 20, high fasting insulin was associated with greater gestational weight gain (multivariate-adjusted predicted mean 39.6, 95% CI 30.9–40.3 lbs for Quartile 4 (Q4) vs. 31.3, 95% CI 28.6–34.1 lbs for Q1) and higher risk of excessive weight gain. By contrast, among women with a BMI of 35, higher fasting insulin was associated with lower total gain (multivariate-adjusted predicted mean 25.7, 95% CI 22.6–28.7 lbs for Q4 vs. 33.2, 95% CI 10.5–55.9 lbs for Q1) and lower risk of excessive gain. Conclusion In our cohort, early pregnancy BMI modified the association between insulin homeostasis and gestational weight gain. These associations suggest that the physiologic consequences of hyperinsulinemia differ between normal weight and obese women.