Editors:Elham Reshid and Hailemariam Shimelis
Metformin is an anti-hyperglycemic agent which improves glucose tolerance in patients with type 2 diabetes. Its pharmacologic mechanisms of action appear to be different from other classes of oral anti-hyperglycemic agents. It decreases hepatic glucose production, decreases intestinal absorption of glucose, and improves insulin sensitivity by increasing peripheral glucose uptake and utilization. This alert will shed light on the current status of metformin’s use during pregnancy.
An accumulating body of evidence strongly suggests that abnormal blood glucose levels during pregnancy are associated with a higher incidence of congenital abnormalities. Most experts recommend that insulin be used during pregnancy to maintain blood glucose levels as close to normal as possible. Metformin was long known to cross the placenta and enter the bloodstream of the fetus. This fact formed the rationale for clinicians to avoid metformin during pregnancy unless clearly needed. Moreover, the lack of adequate and well-controlled studies in pregnant women made clinicians to be hesitant from using metformin during pregnancy.
A systematic review done on the efficacy and safety of metformin during pregnancy in women with gestational diabetes mellitus (GDM) or polycystic ovary syndrome (PCOS) suggests that there are potential advantages for the use of metformin over insulin. In GDM, the advantages for metformin are with respect to maternal weight gain, neonatal outcomes and acceptability. The use of metformin throughout pregnancy in women with PCOS has also been shown to reduce the rates of early pregnancy loss and preterm labor and protect against fetal growth restriction. Moreover, there have been no demonstrable teratogenic effects, intra-uterine deaths or developmental delays with the use of metformin.
Based on this and other studies, the FDA has now classified metformin as a class B medication during pregnancy. A class B medication is considered safe to be administered during pregnancy, though class B rating presupposes that evidence for safety is largely derived from animal studies, as there are limited human studies.
To sum up, there is currently no warning with metformin and pregnancy and is considered to be safe for use. Studies involving metformin and animals have shown no ill effects to the mother pregnancy, or the offspring upon birth.