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.
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.
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.
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.
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