Paternal metformin use during spermatogenesis shows no increased risk for major congenital malformations in over 11 000 children across five countriesNew analysis shows fathers taking metformin did not raise birth defect risks for their children

British journal of clinical pharmacology Published June 1, 2026 Study authors: Damkier Per, van Gelder Marleen M H J, Huybrechts Krista F, Meng Lin-Chieh, Hernandez-Diaz Sonia, Ni… PubMed ↗ DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Paternal metformin use during spermatogenesis is not linked to an increased risk of major congenital malformations in children.

This comprehensive review examined data from five countries to assess potential risks associated with paternal medication use. The study specifically focused on men taking metformin during the period of spermatogenesis leading to conception. Researchers analyzed outcomes for over 11 000 live-born children to determine if exposure influenced developmental health.

The primary investigation centered on the likelihood of major congenital malformations occurring in these offspring. Statistical analysis revealed a pooled risk ratio of 1.03, with a 95% confidence interval ranging from 0.88 to 1.21. This narrow range indicates that the observed risk is statistically indistinguishable from that of the general population.

Consequently, the findings suggest that paternal use of metformin does not elevate the chance of birth defects. These results provide reassurance for men managing type 2 diabetes who are planning to become fathers. The data supports continuing standard treatment without fear of harming the developing fetus through paternal exposure.

Doctors looked at many fathers who used the diabetes drug metformin while making sperm. They wanted to know if this medicine could cause serious birth problems for the baby later on. The team checked records from five different countries to get a clear picture.

They studied more than 11,000 live-born children born to these fathers. The main goal was to see if major birth defects happened more often in this group. The results showed that the risk was about the same as for fathers who did not take the medicine.

The numbers showed a risk ratio of 1.03, which means the risk was basically unchanged. The range of results included both a small drop and a small rise in risk, but nothing serious. This means the medicine is safe for dads planning a family.

Parents with type 2 diabetes can feel better knowing their medicine choice does not hurt their future child. This study gives peace of mind to many families trying to start a new life together.

What this means for you:

Fathers taking metformin before pregnancy did not increase the risk of major birth defects for their children.

Study Details

Study typeMeta analysis

EvidenceLevel 1

PublishedJun 2026

PMID41937475

View Original Abstract ↓

Metformin is the first-line drug for the treatment of Type 2 diabetes. In 2022, a Danish registry-based study reported a 40% increased risk of major congenital malformations following paternal exposure during spermatogenesis. This raised widespread concern about the use of metformin in males of reproductive age. Three subsequent studies were unable to replicate this finding. We performed a meta-analysis of four observational studies with data from five countries covering more than 11 000 live-born children whose fathers used metformin during spermatogenesis. The pooled risk ratio from an inverse variance-weighted random effects model was 1.03 (95% CI 0.88-1.21). We conclude that paternal exposure to metformin does not confer a meaningfully increased risk of major congenital malformations.

Paternal metformin use during spermatogenesis shows no increased risk for major congenital malformations in over 11 000 children across five countriesNew analysis shows fathers taking metformin did not raise birth defect risks for their children

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Paternal metformin use during spermatogenesis shows no increased risk for major congenital malformations in over 11 000 children across five countriesNew analysis shows fathers taking metformin did not raise birth defect risks for their children

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