Lifestyle Health Diabetes Drug Metformin Linked to Increase in Birth Defects in Boys, Study Finds The study found that men’s use of metformin within three months of conceiving is linked to genital defects in boys By Stephanie Wenger Stephanie Wenger Instagram Twitter Stephanie Wenger is a TV Writer/Reporter at PEOPLE. She joined the brand in 2021 as digital news writer, spanning across the site's verticals. She previously contributed to E! Online, HollywoodLife, Discover Los Angeles, Oscar.com and Hollywood.com. She appeared on air at AfterBuzz TV. She began her journalism career as an intern at Good Morning America and Access Hollywood. She graduated from Boston University with a Bachelor's in communications and received a Master's in journalism from the University of Southern California. People Editorial Guidelines Published on March 29, 2022 05:14 PM Share Tweet Pin Email Photo: Getty Fathers' use of diabetes drug metformin is linked to an increase in birth defects in boys, according to a study released by Annals of Internal Medicine on Monday. Researchers from the University of Southern Denmark and Stanford University found the use of the diabetes medication within three months of conception — or during sperm development — increased the risk for genital defects in boys. The findings showed the frequency of birth defects in babies born to men who had a type 2 diabetes but were not using metformin was 3.3% but increased to 5.2% with fathers' exposure to the drug prior to conception. 6 Cases of Birth Defects Caused by Zika Reported in the U.S. as Number of Pregnant Women with Virus Continues to Rise Use of metformin only led to an increased risk of genital birth defects in boys, according to the study. No other birth defects were associated. Men were considered exposed to metformin if they filled a prescription for the drug three months prior to conception. And men who took metformin before or after the three-month period did not show statistically higher risk of their sons having birth defects. Men with diabetes are advised to discuss treatment options with their doctor prior to trying to conceive a child. The study notes that sperm quality is also affected by diabetes control so terminating the use of the metformin may also affect birth outcomes. Biological Mom Decides to Keep Baby Born with Birth Defects After Adoptive Mom Rejects Her: 'She Is My Heart' The researchers used national registries of over 1 million births between 1997 to 2016 to determine the number of birth defects based fathers' use of the diabetes medications. Never miss a story — sign up for PEOPLE's free weekly newsletter to get the biggest news of the week delivered to your inbox every Friday. The study only included babies born to women under 35 and men under 40. Children with mothers who were diagnosed with diabetes were also excluded. 2-Year-Old Boy Adopts Shelter Dog with Same Birth Defect: 'They Instantly Loved Each Other' Researchers did not evaluate other aspects of diabetes such as glycemic control or medication compliance for the study. The U.S. Food and Drug Administration has not released a warning against the use of metformin.