A large study published in BMJ indicates that men taking metformin for type 2 diabetes do not face an increased risk of having children with birth defects. The research, which analyzed data from over 3 million pregnancies in Norway and Taiwan, contradicts earlier concerns raised by a 2022 Danish study. These findings provide reassurance to both clinicians and patients regarding the safety of metformin use in men planning to start a family.
The study, led by Professor Hedvig Nordeng from the University of Oslo, addressed worries stemming from previous research suggesting that metformin could negatively impact sperm quality and potentially lead to congenital malformations. Metformin, a common medication for managing blood sugar levels in type 2 diabetes, has been shown in some studies to lower testosterone levels, raising concerns about sperm health.
Study Details and Findings
The researchers examined data from nearly 620,000 babies born in Norway between 2010 and 2021 and over 2.5 million babies born in Taiwan between 2004 and 2018. In Norway, approximately 5% of babies born to fathers taking metformin had birth defects, compared to 4% in those whose fathers did not use the drug. This difference was not statistically significant. Similarly, in Taiwan, birth defects occurred in about 3% of children, regardless of their fathers' metformin use.
After specifically analyzing fathers with type 2 diabetes and adjusting for other potential influencing factors, the researchers found no elevated risk of birth defects associated with metformin use. This suggests that metformin does not contribute to congenital malformations in offspring.
Implications for Clinical Practice
The study's authors suggest that these results should reassure clinicians when considering metformin as a treatment option for men with type 2 diabetes who are planning a family. The findings support the continued use of metformin as a safe and effective treatment for managing blood sugar levels without increasing the risk of birth defects in children.
Expert Commentary
In an accompanying editorial, Australian researchers acknowledged that while the new findings offer reassurance, some concerns raised by the Danish analyses may persist. They suggest that further confirmatory studies are worthwhile but emphasize that the current study provides valuable reassurance for clinicians and prospective fathers prescribed metformin.
