Association between insulin resistance and preeclampsia in obese non-diabetic women receiving metformin

Objectives: To examine whether the reduced incidence of preeclampsia in non-diabetic obese pregnant women treated with metformin is mediated by changes in insulin resistance.

Methods: This was a secondary analysis of obese pregnant women in a randomised trial (MOP trial). Fasting plasma glucose and insulin were measured in 384 of the 400 women who participated in the MOP trial. Homeostasis model assessment of insulin resistance (HOMA-IR) was compared in the metformin and placebo groups and in those that developed preeclampsia versus those that did not develop preeclampsia.

Results: At 28 weeks, median HOMA-IR was significantly lower in the metformin group. Logistic regression analysis demonstrated that there was a significant contribution in the prediction of preeclampsia from maternal history of chronic hypertension and gestational weight gain, but not HOMA-IR
either at randomisation (p¼0.514) or at 28 weeks (p¼0.643).

Conclusions: Reduced incidence of preeclampsia in non-diabetic obese pregnant women treated with metformin is unlikely to be due to changes in insulin resistance.