In May 2020, the Food and Drug Administration (FDA) recommended that some makers of metformin extended release remove some of their tablets from the U.S. market. This is because an unacceptable level of a probable carcinogen (cancer-causing agent) was found in some extended-release metformin tablets. If you currently take this drug, call your healthcare provider. They will advise whether you should continue to take your medication or if you need a new prescription.

Metformin is a commonly used drug for managing type 2 diabetes. It is considered an effective treatment option for many people with diabetes, but is it safe for pregnant women?

Metformin is a drug that helps to lower blood sugar. It is considered one of the best first line treatments for type 2 diabetes.

A review posted to Diabetology & Metabolic Syndrome notes that metformin helps to lower blood sugar levels, strengthens the endocrine system, improves insulin resistance, and reduces fat distribution in the body.

Before taking any drugs, including metformin, a pregnant woman has to be absolutely sure that the drugs will not affect her or her baby.

[pregnant woman taking pills]Share on Pinterest
Women with type 2 diabetes who already take metformin may be concerned about its effects during pregnancy.

Some people are concerned about using metformin during and after pregnancy because it crosses the placenta. This means that when a pregnant woman takes metformin, so does her baby.

However, the results of the few studies that have been carried out so far into the effects of taking metformin during pregnancy have been positive.

A 2014 review posted to Human Reproduction Update found that the drug did not cause birth defects, complications, or diseases.

The researchers did note, however, that larger studies should be carried out to make this evidence more conclusive.

Metformin and gestational diabetes

A separate review posted to Human Reproduction Update noted that women who took metformin to treat gestational diabetes (diabetes during pregnancy) gained less weight than women who took insulin.

A 2-year follow-up study found that babies born to the women treated with metformin had less fat around their organs, which could make them less prone to insulin resistance later in life.

This could mean that children who are exposed to metformin at a young age could gain long-term benefits. This is only a hypothesis at this stage, and long-term studies will have to be carried out before anything is certain.

Share on Pinterest
Metformin appears to have a positive effect on fertility.

Metformin is commonly used to treat PCOS, or polycystic ovary syndrome. According to research posted to the Journal of Human Reproductive Sciences, women with PCOS, particularly those who are overweight, tend to be insulin resistant.

PCOS can cause missed periods and infrequent ovulation, which may lead to infertility or difficulty in conceiving.

Metformin is used to lower insulin levels by regulating the body’s blood sugar. It also helps regulate menstruation and ovulation. Metformin can reduce the risk of type 2 diabetes or help manage the symptoms for those women who already have the condition.

Because metformin helps ease the symptoms of PCOS, many women find it easier to conceive when on the drug.

Reduced pregnancy problems

According to a review posted to Metabolism: Clinical and Experimental, women with PCOS or with gestational diabetes, who use metformin, appear to have reduced rates of early miscarriage, premature labor, and unhealthy fetal weight, compared with those using insulin.

The researchers noted that the body appears to accept metformin better than insulin. They also noted that metformin caused no developmental delays, fetal deaths in the uterus, or had any disturbing effects on the embryo or fetus during pregnancy. This is promising news for the safety of the drug.

When used correctly, the risks and side effects of metformin are relatively low. Some people do experience mild side effects, however. The most common side effects of metformin are:

For pregnant women, these symptoms may make the feeling of morning sickness worse. It is important to be on the lowest effective dose to help reduce or prevent side effects with metformin.

Metformin can also reduce the blood sugar too much, causing hypoglycemia. Symptoms of hypoglycemia include:

  • weakness and fatigue
  • headache
  • confusion, drowsiness, or dizziness
  • irritation
  • fast heart rate, shaking, feeling jittery
  • hunger
  • sweating or chills

The risks of serious complications, such as lactic acidosis, when lactic acid builds up in the tissues, are also possible with metformin. Lactic acidosis is caused by problems with the metabolism, and symptoms include:

  • strong stomach pains
  • nausea and vomiting
  • irregular heart rate
  • dizziness, weakness, or feeling light headed
  • tiredness or extreme fatigue
  • trouble breathing
  • muscle pains
  • difficulty sleeping or sparse sleep

If a person feels they have any serious symptoms or signs of lactic acidosis, they should contact an emergency medical team immediately.

The dosage of metformin for people with type 2 diabetes varies from person to person. It is based on their medical history, insulin sensitivity levels, and sensitivity to side effects.

Share on Pinterest
The dose of metformin varies depending on the individual. Women should talk to their doctor if they have concerns about taking too much or too little of the drug.

Pregnant women who take insulin for type 2 diabetes may also be prescribed metformin to help with symptoms that develop during pregnancy.

The dosage for women with PCOS also varies based on their reaction to the medication. If side effects cannot be managed, doctors will often try to lower the dose or seek other options.

To minimize side effects, doctors start an individual on very low doses and gradually increase these until their symptoms are in check. When used correctly, the drug is considered to have a high safety profile.

Alternatives to metformin

Pregnant women with gestational diabetes or type 2 diabetes are commonly given metformin during their pregnancy.

If they have an adverse reaction to the drug, changes to their gastrointestinal system, or simply do not wish to take it, there are other options. The most common alternative to metformin is to be treated with insulin alone, which helps to stabilize blood sugar levels.

Outlook for taking metformin during pregnancy

All current research points to the fact that metformin has a low risk of complications during pregnancy, though further clinical trials are still being called for.

Some studies suggest that metformin may even have benefits for pregnant women and their babies when taken correctly.

Doses of any medication should be carefully managed by a doctor, but there is currently little risk to pregnant women or their offspring at all stages of development.

Discover more resources for living with type 2 diabetes by downloading the free app T2D Healthline. This app provides access to expert content on type 2 diabetes, as well as peer support through one-on-one conversations and live group discussions. Download the app for iPhone or Android.