The aim of this study was to measure the capacity of glucose- and weight-related parameters to predict pregnancy-induced hypertensive disorders in women with gestational diabetes.

An observational study was conducted involving 2037 women with gestational diabetes. The associations of glycaemic and weight-related parameters with pregnancy-induced hypertensive disorders were obtained by univariate and adjusted multivariate analyses. Also, model predictability and attributable predictor risk percentages were calculated, and collinearity and factor interactions examined.

Multivariate analyses revealed that hypertensive disorders were mainly predicted by average third-trimester glycated haemoglobin (HbA_1c) levels≥5.9%, by being overweight or obese before pregnancy and by excess gestational weight gain after adjusting for age, tobacco use, chronic hypertension, parity, urinary tract infections and gestational age at delivery. Prepregnancy body weight (overweight and obesity) had the strongest impact on pregnancy-related hypertensive disorders (attributable risk percentages were 51.5% and 88.8%, respectively). The effect of being overweight or obese on hypertensive disorders was enhanced by HbA_1c levels and gestational weight gain, with elevated HbA_1c levels multiplying the effect of being overweight before pregnancy.

The average third-trimester HbA_1c level is a novel risk factor for pregnancy-induced hypertensive disorders in women with gestational diabetes. HbA_1c levels≥5.9%, prepregnancy overweight or obesity and excess gestational weight gain are all independent risk factors of pregnancy-related hypertensive disorders in such women. In treated gestational diabetes patients, the strongest influence on hypertensive disorders is prepregnancy obesity.