Health

Metformin, a widely used diabetes medication, not associated with higher risk of birth defects

Infants born to men or to women taking metformin, a common type 2 diabetes drug, do not appear to be at higher risk of birth defects, according to two new studies led by Harvard Chan School.

June 26, 2024— Infants born to parents using metformin, a widely prescribed medication for managing type 2 diabetes, do not seem to face an increased risk of birth defects, according to two new studies conducted by researchers at the Harvard T.H. Chan School of Public Health.

The findings were published on June 18 in the Annals of Internal Medicine. Ran Rotem, a research associate in the Department of Environmental Health, led the study on paternal use of metformin. Yu-Han Chiu, a former postdoctoral fellow and research scientist in the Harvard Chan Department of Epidemiology’s CAUSALab and now an assistant professor at Penn State College of Medicine’s Division of Epidemiology, spearheaded the study on maternal use.

Earlier research had suggested a link between paternal metformin use and birth defects. To delve deeper into this issue, the researchers analyzed health outcomes for nearly 384,000 infants born in Israel from 1999 to 2020 and reviewed their fathers’ health records. The study revealed that the prevalence of birth defects among infants whose fathers took metformin before conception was 6.2%, compared to 4.7% for those whose fathers did not take the drug. After adjusting for various health factors, including other conditions affecting both parents, the researchers concluded that metformin did not increase the risk of birth defects.

Research on maternal metformin use during early pregnancy has been sparse. To address this gap, the researchers utilized Medicaid data from nearly 12,500 pregnant women in the U.S. with diabetes to assess the risk of birth defects associated with two treatments: insulin alone or a combination of insulin and metformin. Similar to the paternal study, this research found no increased risk from maternal metformin use. The estimated risk of birth defects was 5.7% for women taking both insulin and metformin and 8% for those taking insulin alone.

“Poor blood sugar control is a risk factor for birth defects. Insulin combined with metformin may result in better blood sugar control than using insulin alone, which might explain why we observed a slightly lower risk of congenital malformations when comparing with insulin alone,” Chiu explained in a June 17 CNN article about the studies.

The researchers noted that the higher prevalence of birth defects among infants born to parents with diabetes, observed in previous studies, might be attributed to the parents’ poorer cardiometabolic health rather than the medications used to treat them.

“When considering a medication, it’s important to also consider the underlying conditions it treats,” Rotem told CNN. “Diabetes itself complicates fertility and can lead to complications during pregnancy and in newborns.”

Rotem added, “If diabetes can be managed through lifestyle changes like increased exercise and a healthier diet, that’s beneficial. However, if medication is necessary, metformin appears to be a safe option for both mothers and fathers.”

Read the CNN article: Use of popular diabetes drug in preconception or early pregnancy may not be tied to higher birth defect risk, studies suggest

Photo: iStock/geargodz

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