New research indicates that pregnant women with pre-gestational diabetes who take anti-diabetic medication metformin are at a far higher risk for poor pregnancy outcomes than those who do not. Researchers studied 950 pregnant women and found that 5.1% of those who took metformin for pregestational diabetes experienced major birth defects, compared to 2.1% of those not exposed to metformin during pregnancy and 1.7% who took metformin for other reasons. Findings also revealed that 24% of those with pregestational diabetes who were exposed to metformin had a miscarriage.