Key takeaways:
Insulin is the first-choice medication for managing diabetes during pregnancy. Metformin is an oral medication that may be an option if you’re unable to use insulin.
New research suggests that there may be some benefits to taking metformin for diabetes during pregnancy. These benefits include less weight gain and a lower risk of preeclampsia (a pregnancy complication that causes high blood pressure).
Metformin may raise the risk of small size for infants at birth. More research is needed in order for experts to recommend metformin for most pregnant women with diabetes.
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If you’re pregnant and have Type 2 diabetes, changes to diet and exercise are usually recommended to manage it. This is also the case if you develop diabetes during pregnancy (gestational diabetes, or GD).
But if you’re unable to reach your blood sugar (glucose) goals with diet and exercise alone, medications are often the next step. Insulin is the first-choice medication for managing all types of diabetes during pregnancy.
Metformin is a first-choice medication for many people living with Type 2 diabetes. But unlike insulin, metformin crosses through the placenta during pregnancy. This means the baby is exposed to metformin in the womb. For this reason, metformin is not a first-choice medication for diabetes during pregnancy.
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But recent studies suggest that metformin could be used off-label for diabetes during pregnancy. Let’s discuss what the research says.
What is metformin?
Metformin is an oral medication that’s FDA approved to lower blood glucose for people ages 10 years and older with Type 2 diabetes. It’s best used in combination with diet and exercise changes.
There are a few dosage forms of metformin:
Metformin oral solution
Metformin immediate-release (IR) tablets
Metformin is usually started at 500 mg by mouth twice daily or 850 mg by mouth once daily. This dosage can be slowly raised to a maximum of 2,550 mg per day.
Is it safe to take metformin while I’m pregnant?
Maybe — but more research is needed.
A randomized controlled trial of 400 women and a review of 9 clinical trials looked at the use of metformin in pregnancy. Researchers didn’t find an increase in rates of birth defects with metformin. In both cases, the study authors called for more research regarding metformin’s safety in pregnancy. It's important to note that these studies weren’t conducted with women who had GD. Some studies looked at women at risk of developing GD. Others looked at women who had Type 2 diabetes before they became pregnant.
The American Diabetes Association (ADA) states that insulin is the preferred medication to take for diabetes during pregnancy. This includes women who develop GD and those with existing diabetes. Experts also recommended that women taking metformin to treat polycystic ovary syndrome (PCOS) before conceiving should stop it after becoming pregnant.
What are the benefits of taking metformin while pregnant?
Compared to insulin, pregnant mothers taking metformin have a lower risk of excess weight gain. It’s also easier and more affordable for many women to take metformin instead of insulin.
Other potential benefits of taking metformin for diabetes during pregnancy include:
Better blood sugar control for mothers
Lower risk of severely low blood sugar (hypoglycemia)
Fewer newborns with large birth weights — this helps lower the risk of complications during labor and delivery
A large review of 35 studies and over 8,000 pregnancies looked at the impact of metformin compared to other diabetes medication regimens. They found that women who took metformin during pregnancy had a lower risk of preeclampsia.
Preeclampsia is a pregnancy complication characterized by high blood pressure and increased protein levels in urine. If left untreated, preeclampsia can progress to a more severe problem called eclampsia. Eclampsia can result in seizures and death.
What are the risks of taking metformin while pregnant?
Taking metformin during pregnancy may be linked to low birth weight in newborns. Small-sized infants have risks of certain health issues, like infections and breathing problems. So this is an important consideration when deciding to take metformin during pregnancy.
A large study of over 4,800 children who were exposed to metformin before birth didn’t find an increased risk of long-term problems. There was no difference in rates of obesity, low or high blood sugar, or developmental problems.
However, a review of 28 studies found conflicting results. It reported that children born to mothers who took metformin while pregnant had higher body weights later in childhood. More research is needed to confirm the long-term risks metformin in pregnancy.
Side effects of metformin for pregnant women are usually mild. They often include stomach-related side effects, such as diarrhea, nausea, and vomiting.
What can I take instead of metformin while I’m pregnant?
Glyburide (Diabeta) is another oral diabetes medication. It may also be a possible option for managing GD. In a small study comparing metformin and glyburide in women with GD, no significant difference was found in infant birth weight or low blood sugar in infants. But women taking metformin had less weight gain compared to those taking glyburide.
Another study comparing glyburide and metformin for GD found both medications had similar benefits. Women taking glyburide experienced low blood sugar more often. Those taking metformin had more stomach-related side effects.
What are other things I can do to treat diabetes while I’m pregnant?
The ADA recommends pregnant women eat a healthy diet and exercise more to help manage blood glucose levels. They also encourage women to work with a dietician to develop a nutrition plan that works for them. These lifestyle changes can be made before or after medications are started.
The bottom line
Insulin is still the first-choice medication for treating GD and Type 2 diabetes during pregnancy. Some research suggests that there may be benefits to using metformin during pregnancy. These may include less weight gain and a lower risk of preeclampsia.
Like most medications, metformin does have side effects. And metformin may raise the risk of low birth weight in infants. More research is needed to confirm this risk. But metformin may be a reasonable option if you’re unable to take insulin.
Why trust our experts?
References
American Diabetes Association Professional Practice Committee. (2022). 15. Management of diabetes in pregnancy: Standards of medical care in diabetes—2022. Diabetes Care.
Brand, K. M. G., et al. (2022). Metformin in pregnancy and risk of adverse long-term outcomes: A register-based cohort study. BMJ Open Diabetes Research and Care.
Cassina, M., et al. (2014). First-trimester exposure to metformin and risk of birth defects: A systematic review and meta-analysis. Human Reproduction Update.
Feig, D. S., et al. (2020). Metformin in women with type 2 diabetes in pregnancy (MiTy): A multicentre, international, randomised, placebo-controlled trial. Lancet.
Hyer, S., et al. (2018). Metformin in pregnancy: Mechanisms and clinical applications. International Journal of Molecular Sciences.
Khomami, M. B., et al. (2022). Clinical management of pregnancy in women with polycystic ovary syndrome: An expert opinion. Clinical Endocrinology.
MedlinePlus. (2022). Birth weight.
Nachum, Z., et al. (2017). Glyburide versus metformin and their combination for the treatment of gestational diabetes mellitus: A randomized controlled study. Diabetes Care.
Preferred Pharmaceuticals Inc. (2022). Metformin hydrochloride [package insert].
Silva, J. C., et al. (2010). Metformin compared with glyburide for the management of gestational diabetes. International Journal of Gynaecology and Obstetrics.
Syngelaki, A., et al. (2016). Metformin compared with glyburide for the management of gestational diabetes. New England Journal of Medicine.
Tarry-Adkins, J. L., et al. (2019). Neonatal, infant, and childhood growth following metformin versus insulin treatment for gestational diabetes: A systematic review and meta-analysis. PLOS Medicine.
Tarry-Adkins, J. L., et al. (2021). Impact of metformin treatment during pregnancy on maternal outcomes: A systematic review/meta-analysis. Scientific Reports.
