Hypertension medications are safe for women to take during their first trimester, a new study has revealed.
Previous research has linked the use of beta-blockers, which reduce blood pressure, to congenital malformations such as heart defects, cleft lip and cleft palate because the medications cross the placenta.
But scientists at Brigham and Women's Hospital and Harvard Medical School found that the average risk of babies being born to women who had taken the prescription was less than one percent.
With the rate of mothers with heart problems soaring in the US, the researchers say that not treating high blood pressure could not only jeopardize the health of the mother, but also the health of the baby - even potentially resulting in a miscarriage.
For the study, the team looked at more than the health records of 18,000 women from both five Nordic countries and the Medicaid database in the US.
The women were all listed as hypertensive during their pregnancy and had live-born infants.
Next, the researchers looked at overall congenital malformations and malformations that previous studies have suggested are associated with beta-blocker exposure, including cleft lip, cleft palate and cardiac defects.
They found that the overall risk of babies exposed to beta-blockers in the first trimester was just 12.6 per 1,000.
More specifically, the rates were 8.4 per 1,000 for cardiac malformations, 3.0 for cleft lip or palate, and 4.0 for central nervous system malformations.
On average, this meant that the risk of the babies being born with defects was 0.007 percent - or less than one percent.
In an accompanying editorial, Dr Joel Ray of St Michael's Hospital at the University of Toronto in Canada said the risk to a fetus comes not from the medication itself but from other factors.
'Women with chronic hypertension are more likely than women without hypertension to have higher body mass index, older age, and pre-pregnancy diabetes mellitus, factors which are themselves risk factors for birth defects,' he wrote.
