Metformin Continuation in Pregnancy Minimally Affects Nonlive Birth

A study published on June 18, 2024, in the Annals of Internal Medicine reveals that continuing metformin treatment and adding insulin during early pregnancy does not significantly impact the risk of nonlive births or congenital malformations compared to switching to insulin monotherapy. This observational cohort study was led by Dr. Yu-Han Chiu from the Harvard T.H. Chan School of Public Health in Boston.

The research included 12,489 pregnant women with pregestational type 2 diabetes who were on metformin monotherapy before their last menstrual period (LMP). The study compared two treatment approaches: insulin monotherapy, where metformin was discontinued, and insulin was introduced within 90 days of the LMP (850 women), and a combination of insulin plus metformin, where metformin was continued alongside the introduction of insulin within the same timeframe (1,557 women).

The findings indicated that the risk of nonlive births was 32.7% for those on insulin monotherapy and 34.3% for those on the combined treatment of insulin and metformin. This translated to a risk ratio of 1.02, with a 95% confidence interval ranging from 1.01 to 1.04. In terms of live births with congenital malformations, the risk was 8.0% for the insulin monotherapy group and 5.7% for the insulin plus metformin group. The risk ratio for this outcome was 0.72, with a 95% confidence interval between 0.51 and 1.09.

The research team highlighted that current recommendations advising the switch from metformin to insulin before pregnancy due to concerns about teratogenicity might need to be re-evaluated. The data suggests that continuing metformin along with insulin initiation does not increase the risk of adverse pregnancy outcomes compared to solely using insulin.

This study's insights are crucial for medical professionals managing type 2 diabetes in pregnant women, as they provide evidence that could influence treatment guidelines and practices. The ability to continue metformin during pregnancy, combined with insulin, could offer a more flexible and potentially beneficial treatment strategy without increasing the risk of nonlive births or congenital malformations.