Metformin in Pregnancy — Is It Safe?
Last reviewed: · Source: US FDA drug label database
Metformin is sometimes continued or started in pregnancy for gestational diabetes — but requires close medical supervision.
Is it safe to take Metformin with Pregnancy?
Metformin is used in pregnancy for two main reasons: continuing treatment in women with type 2 diabetes who become pregnant, and treating gestational diabetes. It crosses the placenta, but decades of use have not revealed a clear pattern of birth defects. NICE recommends metformin as a first-line oral treatment for gestational diabetes when diet alone is insufficient. However, it is not universally used in all countries, and insulin is often preferred for better glucose control. Always follow your diabetes team's guidance.
How do Metformin and Pregnancy interact?
Metformin inhibits hepatic gluconeogenesis and improves insulin sensitivity. It crosses the placenta — fetal blood levels are approximately 50% of maternal. Long-term safety data from trials like MiG (Metformin in Gestational Diabetes) and follow-up studies suggest no major teratogenic risk, though some research suggests possible effects on offspring metabolic outcomes that are still being evaluated.
Data sourced from the US Food and Drug Administration (FDA) drug label database: NICE guideline NG3 — diabetes in pregnancy; OpenFDA metformin drug label.
Who should be careful?
Women with gestational diabetes or pre-existing type 2 diabetes. Metformin should only be taken in pregnancy under medical supervision. Women planning pregnancy who take metformin for PCOS should discuss continuation with their GP.
What if I've already taken Metformin and Pregnancy?
If you are taking metformin as prescribed for diabetes or gestational diabetes, continue as directed. Do not stop without speaking to your diabetes team.
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Frequently Asked Questions
Is metformin safe during pregnancy?
Metformin is used in pregnancy for gestational diabetes and pre-existing type 2 diabetes under medical supervision. It has a long safety record but crosses the placenta. Always take it only as prescribed.
Should I stop metformin when pregnant?
Do not stop without medical advice. Women with gestational diabetes or type 2 diabetes often need to continue metformin — stopping could lead to poorly controlled blood sugar, which is harmful to the baby.
Can metformin cause birth defects?
Decades of use have not established a clear pattern of birth defects from metformin. It is considered one of the safer oral diabetic agents in pregnancy, though monitoring is still required.
I take metformin for PCOS — should I keep taking it in pregnancy?
Discuss this with your GP or obstetrician as soon as you know you are pregnant. Some women with PCOS continue metformin in early pregnancy; this decision should be individualised.