Pregnancy: Pregnancy Risk Factor: B.
Pregnancy Considerations: Adverse events have not been observed in animal studies; therefore, metformin is classified as pregnancy category B. Metformin has been found to cross
the placenta in concentrations which may be comparable to those found in the maternal plasma. Pharmacokinetic studies suggest that clearance of metformin may be increased during pregnancy and dosing may need adjusted in some women when used during the third trimester.
Fetal, neonatal, and maternal outcomes have been evaluated following maternal use of metformin for the treatment of GDM and type 2 diabetes. Available information suggests that metformin use during pregnancy may be safe as long as good glycemic control is maintained; however, many studies used metformin during the second or third trimester only. Maternal hyperglycemia can be associated with adverse effects in the fetus, including macrosornia, neonatal hyperglycemia, and hyperbilirubinemia; the risk of congenital malformations is increased when the HbA1c is above the normal range. Diabetes can also be associated with adverse effects in the mother. Poorly-treated diabetes may cause end-organ damage that may negatively affect obstetric outcomes. Physiologic glucose levels should be maintained prior to and during pregnancy to decrease the risk of adverse events in the mother and the fetus. Until additional safety and efficacy data are obtained, the use of oral agents is generally not recommended as routine management of GDM or type 2 diabetes mellitus during pregnancy. Insulin is the drug of choice for the control of diabetes mellitus during pregnancy.
Lactation: This product enters the breast milk and is not recommended for lactating women.