Metformin is a drug frequently used for diabetes treatment during pregnancy but its effects are not well understood. Butalia and colleagues reviewed existing clinical trials and found some positive effects, and no negative effects, of metformin use during pregnancy.


Metformin is a drug used to treat type 2 diabetes, a disease in which the body becomes unresponsive to insulin. Insulin is a hormone that helps the body store sugar from food and move it into fat and muscles for later use. People with Type 1 diabetes do not produce insulin period and cannot put on weight. People with Type 2 diabetes become resistant to the effects of insulin. This means that the insulin becomes less and less effective over time.

Besides helping us use the energy in the food we eat, insulin also drives many aspects of fertility. Hormones like estrogen or testosterone respond to the amount of insulin in the blood stream. This can influence things like the onset of puberty – high levels of insulin can result in early puberty, for example. As a result, doctors use metformin to treat many fertility-related conditions. This includes infertility and polycystic ovary syndrome. Metformin is also used to treat gestational diabetes – diabetes that occurs during, and as a result of, pregnancy.

Yet, the effects of metformin during pregnancy are not well understood. This is particularly troubling as metformin may affect the developing fetus. Butalia and colleagues published a paper in Diabetic Medicine in which they reviewed 16 existing clinical studies to gain a better understanding of the effects of metformin on pregnant mothers and their babies. These 16 studies totaled 2165 individuals. All the studies compared women on metformin treatment to women on insulin treatment.

Butalia and colleagues found no differences in the rates of either preterm birth or fetal malformations between the two treatment groups. Metformin lowered the risk of low blood sugar in newborns and reduced rates of admission to the neonatal intensive care unit (NICU). Low blood sugar can result in seizures and loss of consciousness.

Metformin also did not increase the risk of death in mothers or babies or result in increased rates of Caesarian section.  While metformin lowers the risk of high blood pressure, it did not affect rates of pre-eclampsia. Additionally, pregnancy weight gain was lower in mothers who received metformin.

Metformin reduced the risk of high birth weight babies but did not affect the rate of low birth weight. Newborns with high birth weights tend to be at increased risk of injury during birth and make birth more difficult for the mother. Heavy babies are also at risk of obesity and diabetes later in life.

Children whose mothers had received metformin during pregnancy were larger and heavier at 18 months than those whose mothers had received insulin. However, the two groups showed no cognitive differences.

Butalia and colleagues conclude that metformin is a safe insulin alternative for diabetes treatment during pregnancy. Unfortunately, each of the studies used by Butalia and colleagues had small sample sizes. In the future, we’ll also need long-term studies on the effects of metformin in children of these mothers.


Written By: C. I. Villamil

Facebook Comments