Continuing metformin during first trimester does not increase risk for major malformations

Continuing metformin during first trimester does not increase risk for major malformations

Abstract: https://www.acpjournals.org/doi/10.7326/M23-2038    

URL goes live when the embargo lifts       

A study of more than 12,000 pregnant women with type 2 diabetes receiving metformin monotherapy before conception found that compared with switching to insulin monotherapy, continuing metformin and adding insulin in early pregnancy resulted in little to no increased risk for major malformations in the infant. The analysis is published in Annals of Internal Medicine.  

Researchers from Harvard T.H. Chan School of Public Health use real-world data from the U.S. Medicaid health care administration database from 2000 to 2018 to evaluate the teratogenicity of metformin use in the first trimester of pregnancy. Women taking metformin were either switched to insulin monotherapy  or prescribed insulin in addition to metformin within 90 days of last menstrual period (LMP). Outcomes considered were non-chromosomal fetal malformations and non-live births, comprised of spontaneous abortion, termination and stillbirth. The estimated risk for non-live birth was 32.7% under insulin monotherapy and 34.3% under insulin plus metformin. The authors also found that the estimated risk for live birth with congenital malformations was 8.0% under insulin monotherapy and 5.7% under insulin plus metformin. Based on these findings, current recommendations that suggest switching from metformin to insulin before pregnancy for fetal safety concerns may require reconsideration. 

Media contacts: For an embargoed PDF, please contact Angela Collom at [email protected]. To speak with the corresponding author, Yu-Han Chiu, MD, ScD, please contact Todd Datz at [email protected].