PCOS - Metformin and Birth Defects
By Samuel Thatcher, MD, Ph.D.

Q. Will metformin (diabex 500mg) cause birth defects? I take metformin for type two diabetes and I also have PCOS. (6 years)

A. There is a clear relationship between how well the blood sugar levels are controlled and the risk of birth defects and overall complication in pregnancy outcome. Blood sugars must be normalized before a pregnancy is attempted.

Metformin is listed as "pregnancy category B" by the FDA. This indicates there is no known relationship with birth defects, but also that it is not proven to be safe. If you have type 2 diabetes and are using metformin, it may be reasonable to continue because pregnancy often worsens insulin resistance. Pregnancy planning clearly needs some advanced thought and conversation with your endocrinologist and possibly a maternal fetal medicine specialist.