The drugs taken for hypertension - angiotensin-converting enzyme (ACE) inhibitors - are known to have a toxic effect on unborn babies during the second and third trimesters.
Now new research from California has looked into whether taking ACE inhibitors in the first trimester can cause birth defects.
Researchers from the Kaiser Foundation Research Institute studied the health records of 465,754 pairs of mothers and infants between 1995 and 2008.
One in 200 mothers had a baby with some sort of birth defect.
The research shows that, for those with hypertension, the risk was increased to 1.25 in 200.
The study, published in the
BMJ, concludes that the drugs did not cause defects, but the underlying hypertension itself could increase the risk.
Professor James Walker, senior vice-president of RCOG, said the study suggests hypertension is associated with a ‘slightly increased risk’ of birth defects.
But added the risks are small compared to those posed by smoking and excessive alcohol consumption.
