Taking Metformin During Pregnancy

Metformin is a drug that is often prescribed, off-label, for the treatment of PCOS and for regulating ovulation. It belongs to a class of drugs that improves the cells' 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.

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 that are insulin resistant, may see more regular periods from taking metformin as well.

Dosage

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 upset stomach, nausea, and diarrhea—especially with higher doses.

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

It is important to take your medication exactly as prescribed and let your doctor 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

Unfortunately, women with PCOS are at a higher risk of developing gestational diabetes (diabetes in pregnancy). Research does support the use of metformin for reducing the risk for gestational diabetes in women with PCOS.

Safety in Early Pregnancy

Knowing that the drug may actually help protect you from pregnancy loss, the next question is often about safety. The studies are encouraging: 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 normal U.S. infant population.

If you are planning on becoming pregnant while taking metformin, make sure to talk to your doctor beforehand about what they want you to do once you get a positive pregnancy test. Even though metformin is a category B drug, meaning that it is relatively safe in pregnancy, it is best to speak with your doctor and follow their instructions. Keep in mind, every doctor is different and has their own opinion on what is right for you and your baby.

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Article Sources
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  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. May 28, 2020

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