Vitamin D insufficiency, excessive weight gain, and insulin resistance during pregnancy.

Background And Aims: Vitamin D insufficiency has been related to metabolic complications during pregnancy, including insulin resistance. There is evidence that excessive weight gain can negatively influence 25-hydroxyvitamin D (25(OH)D) concentrations. We aimed to investigate the association of vitamin D insufficiency during pregnancy (25(OH)D < 75 nmol/L in the second and third trimesters) with insulin resistance, and explore whether excessive gestational weight gain (GWG) could modify such relationship.

Methods And Results: A prospective longitudinal analysis was conducted within the MINA-Brazil Study among 444 pregnant women enrolled in antenatal care and with complete data on 25(OH)D, weight gain, insulin, and homeostatic model assessment of insulin resistance (HOMA-IR). Quantile and logistic regression models were conducted with adjustment for sociodemographic, obstetric, and lifestyle characteristics, as well as gestational age and seasonality at outcome assessment. Predicted probabilities for insulin resistance (HOMA-IR>2.71) were estimated according to excessive GWG. Persistent vitamin D insufficiency was associated with increasing insulin concentrations (p for trend = 0.04); pregnant women with vitamin D insufficiency in the second or third trimester had an odds ratio of 1.83 (95% confidence interval (95% CI) = 1.03, 3.27) for insulin resistance, with significant modification by GWG (p = 0.038). Among participants without excessive GWG, the predicted probability for insulin resistance was 0.345 (95% CI = 0.224, 0.467) for those with persistent vitamin D insufficiency, and 0.134 (95% CI = 0.046, 0.221) for those who were sufficient in vitamin D. Probabilities for insulin resistance did not vary according to vitamin D status among participants with excessive GWG.

Conclusion: Vitamin D insufficiency was associated with insulin resistance in the third trimester of pregnancy, dependent on excessive GWG.