Taking Metformin During Pregnancy

Metformin is often prescribed off-label for the treatment of polycystic ovary syndrome (PCOS) and for regulating ovulation. It belongs to a class of drugs that improves the body's response to insulin and regulates blood sugar.

An off-label prescription means that the U.S. Food and Drug Administration (FDA) has not approved the use of a drug specifically for that condition. In this case, metformin has been approved for the treatment of diabetes but not for PCOS specifically.

Pregnant woman with medication
Andersen Ross / Getty Images

How Metformin Works

Because so many women with PCOS also have insulin resistance and diabetes, it is believed that treating insulin dysfunction might have an effect on the other hormonal irregularities associated with the condition. While researchers aren’t sure of the exact mechanism, there is some evidence that backs up this theory.

Some studies have shown that women who take a combination of metformin and Clomid (a drug that is used to induce ovulation in anovulatory women) have a better response to the medication regimen than those who take Clomid alone. Some women with PCOS, especially those who are insulin resistant, may see more regular periods from taking metformin as well.


Dosages of between 1,500 milligrams (mg) to 2,000 mg daily are typical, depending on a woman's insulin resistance and risks of side effects. Many women taking metformin report having an upset stomach, nausea, and diarrhea—especially with higher doses.

Your healthcare provider may recommend slowly increasing your dosage, rather than starting with the recommended amount from the start, to increase your tolerance to the drug. Other practitioners will recommend the extended-release form, meaning that a small amount of the medication is released throughout the day instead of all at once.

It is important to take your medication exactly as prescribed and let your healthcare provider know if you are experiencing any side effects.

May 28, 2020: The FDA has requested that manufacturers of certain formulations of metformin voluntarily withdraw the product from the market after the agency identified unacceptable levels of N-Nitrosodimethylamine (NDMA). Patients should continue taking their metformin as prescribed until their health professional is able to prescribe an alternative treatment, if applicable. Stopping metformin without a replacement can pose serious health risks to patients with type 2 diabetes.

Early Pregnancy Loss

In addition to difficulty becoming pregnant, women with PCOS may be at risk for pregnancy loss. This is due to an imbalance of hormones and higher levels of insulin.

Several studies have shown a dramatically lower rate of pregnancy loss in women with PCOS taking metformin compared with women who were not taking metformin.

Gestational Diabetes

Women with PCOS are at a higher risk of developing gestational diabetes (diabetes in pregnancy). Research supports the use of metformin for reducing the risk of gestational diabetes in women with PCOS.

Safety in Early Pregnancy

So far, metformin has not been linked to any major birth defects or fetal malformations when taken during the first trimester.

According to a study published in Human Reproduction, babies who were born to mothers who took metformin showed no differences in birth weight, length, growth, or motor-social development during the first 18 months of life compared with the rest of the U.S. infant population.

And another study compared the use of metformin with insulin during pregnancy. The researchers reported that the proportion of newborns admitted to the neonatal intensive care unit (NICU) was significantly lower for those whose mothers took metformin while pregnant when compared with those whose mothers took insulin while pregnant

If you are planning on becoming pregnant while taking metformin, make sure to talk to your healthcare provider beforehand about what they want you to do once you get a positive pregnancy test.

Even though metformin appears to be relatively safe to use during pregnancy, it is always best to follow your practitioner's instructions for you.

5 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Lindsay RS, Loeken MR. Metformin use in pregnancy: promises and uncertaintiesDiabetologia. 2017;60(9):1612–1619. doi:10.1007/s00125-017-4351-y

  2. Hyer S, Balani J, Shehata H. Metformin in Pregnancy: Mechanisms and Clinical ApplicationsInt J Mol Sci. 2018;19(7):1954. Published 2018 Jul 4. doi:10.3390/ijms19071954

  3. U.S. Food and Drug Administration. FDA Alerts Patients and Health Care Professionals to Nitrosamine Impurity Finding in Certain Metformin Extended-Release Products.

  4. Glueck CJ, Goldenberg N, Pranikoff J, Loftspring M, Sieve L, Wang P. Height, weight, and motor-social development during the first 18 months of life in 126 infants born to 109 mothers with polycystic ovary syndrome who conceived on and continued metformin through pregnancy. Human Reprod. 2004;19(6):1323-1330. doi:10.1093/humrep/deh263

  5. Shah MK, Shah MA, Shah SD, Shah PK, Patel K, Gupta M. Comparison of neonatal and maternal outcomes of anti-diabetic drugs in the treatment of gestational diabetes mellitus: Findings from Bayesian network meta-analysis. J Family Med Prim Care. 2022 May;11(5):1610-1618. doi:10.4103/jfmpc.jfmpc_1319_21

Additional Reading

By Nicole Galan, RN
Nicole Galan, RN, is a registered nurse and the author of "The Everything Fertility Book."