Glycemia and its relationship to outcomes in the MiG trial

Abstract

Objective: To determine how glucose control in women with GDM treated with metformin and/or insulin influenced pregnancy outcomes.

Research, Design and Methods: Women randomized to metformin or insulin treatment in the Metformin in Gestational diabetes (MiG) trial had baseline glucose tolerance test (OGTT) results and HbA1c documented, together with all capillary glucose measurements during treatment. In the 724 women who had glucose data for analysis, tertiles of baseline glucose values and HbA1c, and of mean capillary glucose values during treatment, were calculated. The relationships between maternal factors, glucose values and outcomes (including a composite of neonatal complications, preeclampsia and large and small for gestational age (LGA, SGA) infants) were examined with bivariable and multivariate models.

Results: Baseline OGTT did not predict outcomes, but HbA1c predicted LGA (p=0.003). During treatment, fasting capillary glucose predicted neonatal complications (p<0.001) and postprandial glucose predicted preeclampsia (p=0.016) and LGA (p=0.001). Obesity did not influence outcomes and there was no interaction between glycemic control, randomized treatment or maternal BMI in predicting outcomes. The lowest risk of complications was seen in the lowest tertile when fasting capillary glucose was <4.9mmol/l (mean(SD)=4.6(0.3)mmol/l) compared with 4.9-5.3mmol/l or higher and when postprandial glucose was <6.5mmol/l (mean(SD)=6.2(0.2)mmol/l)

Conclusions. Glucose control in women with GDM treated with metformin and/or insulin is strongly related to outcomes. Obesity is not related to outcomes in this group. Targets for fasting and postprandial capillary glucose may need to be lower than currently recommended.