Insulin and the "thrifty" woman: the influence of insulin during pregnancy on gestational weight gain and postpartum weight retention.

OBJECTIVES: To test Neel's hypothesis among pregnant women: a high maternal insulin concentration in early pregnancy increases the risk of weight gain, overweight, and obesity among nondiabetic, low-income gravidas of racial and ethnic minority groups from Camden, New Jersey. METHODS: Fasting insulin was obtained from 461 gravidas at entry to prenatal care. Insulin quartile was related to rate of gestational weight gain and excess weight gain during pregnancy (> or = 90th percentile) and to retained weight and excess weight retention at 4-6 weeks postpartum (> or = 90th percentile). The relationship between excess retained weight and excessive insulin increase (> or = 90th percentile) was also examined. RESULTS: Compared with gravidas with an insulin concentration in the lowest three quartiles, gravidas with the highest insulin quartile had a significantly higher rate of gestational weight gain (nonobese women only) and average weight retained postpartum (all women). Compared with an insulin concentration in the lowest three quartiles, the highest insulin quartile was associated with a 2.05-fold (95% confidence interval [CI] = 1.07-3.93) risk of an excessive rate of gestational weight gain and a 3.58-fold (95% CI = 1.87-6.84) risk of excess weight retained postpartum. Excess weight retained postpartum was linked to a 2.63-fold (95% CI = 1.00-6.89) risk of an excessive increase in insulin concentration postpartum. CONCLUSIONS: Our results support Neel's hypothesis and suggest that a high maternal insulin concentration is associated with increased gestational weight gain and increased weight retention postpartum. High insulin concentration may contribute to pregnancy-related changes in weight and thus may be linked to maternal overweight and obesity postpartum as well as to future risk of gestational and Type 2 diabetes mellitus.