Metformin may be as safe as insulin to treat diabetes during pregnancy

• Researchers have concluded that the oral diabetes medication metformin is just as safe for babies and their pregnant mothers as using insulin.
• The study tracked the long-term health of 10,117 children-mother pairs for up to 11 years postpartum.
• Experts say that metformin and insulin can also be used together to help women with type 2 diabetes and gestational diabetes manage blood glucose levels during pregnancy.

Metformin is just as safe to use during pregnancy to treat type 2 diabetes as insulin, according to new research presented at the Endocrine Society’s ENDO 24 annual meeting this weekend.

The study , which hasn’t been published yet in a peer-reviewed journal, tracked health data and potential long-term side effects of using metformin during pregnancy for up to 11 years postpartum.

Blood glucose levels during pregnancy play a significant role in the development and safety of a fetus in utero and on delivery day.

While today’s popular GLP-1 medications, such as Ozempic , are not approved yet for use during pregnancy, metformin and insulin have been used during pregnancy for decades.

Metformin has been prescribed to people with type 2 diabetes across the globe for more than 60 years — including pregnant women. While metformin is a simpler medication, insulin has been the go-to choice for diabetes management during pregnancy because it cannot cross the placenta, which means it poses no direct risk to the fetus.

Metformin is the simplest non-insulin diabetes medication approved for use during pregnancy because it cannot cause hypoglycemia. Still, research on the long-term effects on children born to women taking metformin has been limited. Past research has only tracked the health of these children and their mothers for about five years.

Learning how to dose insulin is also significantly complicated and stressful, particularly when thrust upon women during pregnancy. Insulin requires multiple daily injections, careful carbohydrate counting, and frequent adjustments. Insulin can also contribute to weight gain.

Metformin, meanwhile, is a pill generally taken two to three times per day. Metformin is less likely to lead to weight gain. While generally considered safe overall for managing diabetes, the safety of a medication during pregnancy calls for a different review.

Details on the study of metformin vs. insulin during pregnancy

For their study, researchers from the Center for Endocrinology, Diabetes, Arthritis & Rheumatism in New Delhi, India, examined data from 10,117 children-mothers pairs, comparing long-term health variables of pregnancies involving metformin versus insulin to manage type 2 diabetes.

The outcomes they considered included body mass index (BMI), waist circumference, total body fat percentage, belly fat percentage, and liver fat percentage. They also tracked obesity and diabetes rates in both children and their mothers.

Researchers said they found no increase in the incidence of these factors in children born to mothers with diabetes who took metformin during pregnancy compared to mothers taking insulin.

This research is considered important because obesity rates are especially high in women and continuing to increase, according to past research . It’s estimated that one in five women have obesity at the time of becoming pregnant — increasing their risk of developing type 2 diabetes during or after pregnancy.

Obesity and diabetes during pregnancy are already associated with some pregnancy complications, including an increased risk of needing a cesarean section, babies born overweight, complicated vaginal births, and postpartum obesity rates in the mother.

Research has established that high blood glucose levels during pregnancy increase the mother’s risk of complications such as preeclampsia , and the baby’s risk of birth defects, jaundice, hypoglycemia, difficulty breathing, premature birth, and stillbirth.

The benefits of taking insulin and metformin during pregnancy

“Overall, it’s lovely that they show metformin is a valid option in pregnancy,” said Jennifer Smith , RD, CDCES, a registered dietitian and coauthor of the book “ Pregnancy with Type 1 Diabetes .”

“What I don’t love about this study is that they make it sound almost like you can choose one over the other and that just isn’t the case,” Smith, who wasn’t involved in the new study, told Medical News Today .

Metformin has a significantly gentler impact on blood glucose levels, explained Smith. She added that determining which medication — metformin and/or insulin — is appropriate should be based on multiple factors beyond the mother’s diabetes diagnosis.

“Starting with metformin may be the best option if the mother has only made lifestyle changes in her diet and exercise habits thus far,” said Smith. “However, each woman’s journey will be different and lifestyle changes may not be enough to bring blood glucose levels down to a safe level for pregnancy.”

This is when insulin may be critical — in addition to metformin.

“If metformin isn’t enough, then insulin can be added, but it wouldn’t necessarily replace the metformin,” said Smith.

How insulin, metformin work

Insulin and metformin work dramatically differently.

Insulin helps the cells throughout your body make use of the glucose in your bloodstream. Metformin, on the other hand, primarily tells your liver to produce less glucose and makes your cells more sensitive to insulin.

By combining these medications, Smith said the impact can significantly improve blood glucose levels. Metformin can help a woman during her pregnancy by reducing liver glucose release and increasing overall insulin sensitivity.

“It should be specified, though, that a woman who is on insulin prior to conception should not change to only taking metformin,” cautioned Smith.

“If she needed insulin to manage her blood glucose levels during pregnancy, she will likely need insulin throughout her pregnancy, too. Metformin can be added to help with blood glucose management, but it wouldn’t be adequate on its own,” she added.

Smith is a pregnancy coach at Integrated Diabetes Services for women with type 1 and type 2 diabetes, but she also knows firsthand how much work blood glucose management during pregnancy can be.

“Managing diabetes during pregnancy isn’t easy,” said Smith. “It’s a labor of love.”