According to a new study recently released from Denmark, commonly used diabetes drugs have been linked to crucial birth defects in the offspring of male patients who were taking it ahead of the babies being conceived.
Around 120 million people are said to have been prescribed the drug across the globe.
Metformin is one the most widely and often initially prescribed treatments for type 2 diabetes, was connected with a 1.4 times greater risk of congenital disabilities in boys whose fathers were taking the drug compared with those born to fathers who were not, researchers from the University of Southern Denmark and Stanford University in the United States found.
In both groups, the mothers had no history of diabetes or hypertension.
The study’s authors, as well as independent experts, pointed to several key limitations of the data published in the Annals of Internal Medicine.
Researchers did not know whether the fathers took the medication as prescribed, or if they had worse control of their diabetes, which could also be linked to a higher risk of birth defects. The study showed that the risk for babies born to men taking insulin rather than metformin were not increased.
Channa Jayasena, head of andrology at Imperial College London, who was not involved in the work, called the results “thought-provoking but inconclusive”.
“Men with diabetes should not be dissuaded from taking metformin, but this is worth looking at more closely,” he added.
It is usually prescribed when diet and physical activity are not enough to control blood sugar levels and typically before more expensive branded diabetes drugs. It works to improve how the body handles insulin.
In the study of 1,116,779 births in Denmark from 1997 to 2016, the researchers found that 5.2% of babies born to men who had been taking metformin had birth defects, particularly genital defects in boys. Among the rest of the population, the rate was 3.3%.
Babies were considered to be exposed to a diabetes drug, including metformin or insulin, if the father had filled at least one prescription during the three months before conception, when the fertilizing sperm were developing.
The researchers said more study was needed, but suggested that men taking metformin consider switching to another treatment when trying to conceive.