Paternal intake of Metformin and birth defect in boys are interlinked: Study

Male children of fathers who took metformin, an antidiabetic drug, were found to have 3.4 times higher incidences of genital and urinary birth defects, a recent study has found. The defects included issues like urethral problems and undescended testicles. Diabetes is an increasing problem in people of reproductive age and the disease itself can deteriorate the quality of sperms in turn causing fertility issues. However, a recent study shows the treatment of diabetes causes fertility issues rather than the disease itself.

Researchers from the University of Southern Denmark and Stanford University studied data from nationwide national registries of births, patients, and prescriptions to evaluate whether the risk for birth defects varied among offspring born to men treated with insulin, metformin, or sulfojnylureas prior to conception. Babies were considered exposed to a diabetes drug if their father filled at least 1 prescription during the 3 months when the fertilizing sperm were developing.

The researchers compared birth defects in the babies across diabetes drugs, different times of taking the drug relative to the development of fertilizing sperm, and with unexposed siblings of the babies. Babies whose fathers took insulin had no increased risk for a birth defect compared with the general group. Babies whose fathers took metformin had an increased risk for birth defects. There were too few babies whose fathers took sulfonylureas to determine risks for birth defects with any certainty. Taking metformin before or after sperm development did not increase the risk for birth defects. Unexposed siblings were also not at increased risk. According to the authors, the size of the diabetes pandemic suggests that treatment of prospective fathers with diabetes, including pharmacologic management and counseling on diet, physical exercise, and weight loss, should be subject to further study.

An editorial from Germaine M. Buck Louis, Ph.D., MS at George Mason University emphasizes the importance of corroborating the findings, given the prevalence of metformin use as first-line therapy for type 2 diabetes. The author also calls for guidance from clinicians to help couples planning pregnancy weigh the risks and benefits of paternal metformin use relative to other medications.