Metformin Linked to Lower Preterm Birth Odds in High-Risk Pregnancy

What Happened

A Monash University-led research team reported that metformin use during pregnancy was associated with fewer early deliveries in mothers described as being at high metabolic risk.

The findings were published in NEJM Evidence and came from a patient-level meta-analysis that pooled data from multiple randomized, placebo-controlled trials.

The analysis asked whether metformin, an oral prescription medication used to manage blood sugar, could prevent gestational diabetes and other adverse pregnancy outcomes, including early birth.

What the Evidence Shows in This Study

The researchers analyzed individual patient data from seven randomized, placebo-controlled trials covering 2,297 pregnancies labeled as high metabolic risk, including higher body weight, insulin resistance, or polyendocrine metabolic ovarian syndrome (PMOS, previously known as PCOS).

According to lead author Aya Mousa, women taking metformin had 35% lower odds of giving birth prematurely before 37 weeks compared with placebo, and the rate of births before 34 weeks was 2.2% with metformin versus 4.4% with placebo.

Among participants who did deliver prematurely, pregnancy length was prolonged by an average of 11 days for women on metformin.

How This Fits With Metabolic Health and Pregnancy Risk

The study focused on pregnancy outcomes in people with higher metabolic risk, a group that can include insulin resistance and higher body weight, which are also common concerns for readers tracking metabolic health markers.

The paper reported that metformin did not prevent gestational diabetes overall, even though it was associated with fewer preterm births in this pooled analysis.

The article notes that gestational diabetes is characterized by elevated blood sugar during pregnancy and affects one in five pregnant women in Australia, and that in severe cases it can trigger premature labor.

• Preterm birth is defined in the report as delivery before 37 weeks.
• The article describes preterm birth as a leading cause of mortality and morbidity for mothers and babies.
• In Australia, the report says more than 26,000 babies (around 8% of all births) are born prematurely each year, with risks that can include respiratory distress, developmental complications, and prolonged neonatal intensive care stays.

Other Outcomes Reported

In this analysis, metformin did not affect several other pregnancy outcomes that were assessed.

The researchers reported no effect on birth weight, high blood pressure, pre-eclampsia, induction of labor, or cesarean section.

The team also described the work as part of the broader Metformin in Pregnancy Study (MiPS) collaboration, which compiles individual trial data to examine metformin use during pregnancy.

Limitations and Open Questions

The authors emphasized that the preterm birth finding needs confirmation in trials that are specifically designed to study preterm birth as an outcome.

They also pointed to unresolved practical questions, including the optimal timing for starting metformin in pregnancy for this purpose.

The report adds that metformin’s long-term impacts during pregnancy continue to be studied, and the broader MiPS collaboration is investigating long-term outcomes of metformin exposure during pregnancy.