LOS ANGELES -- Some blood pressure drugs previously thought to be safe when taken early in pregnancy now appear to substantially raise the risk of major birth defects, doctors say.
Babies whose mothers took ACE inhibitors in their first trimester were more than twice as likely to be born with serious heart and brain problems than those not exposed to any pressure-lowering medicines, a large study in Tennessee found. Other types of blood pressure drugs did not raise the risk to babies.
The research raises troubling questions about the lack of safety data for many drugs prescribed to pregnant women.
About 8 percent of pregnant women develop high blood pressure, which can lead to a heart attack or stroke.
Exactly how many pregnant women take ACE inhibitors or other blood pressure medication is unclear. However, a national survey found the number of ACE inhibitor prescriptions given to women of childbearing age increased from 1.4 million in 1995 to 2.7 million in 2002, the latest data available.
ACE inhibitors -- an acronym for angiotensin-converting enzyme, the chemical explanation of how the drug functions -- already carry a strong Food and Drug Administration ``black box" warning about their dangers in the later stages of pregnancy, and the label says the drugs should be discontinued when pregnancy is detected. But little has been known about their early effects.
Based on the new findings, taking these drugs during early pregnancy ``cannot be considered safe and should be avoided," Dr. William Cooper, a Vanderbilt University pediatrician and the study's lead researcher, said in today's New England Journal of Medicine.
The FDA said more research is needed before it considers changing the warning label to specifically include the risks during the first trimester. But the agency is notifying doctors and patients about the dangers through its website.
Doctors said expectant mothers should not stop treatment, because uncontrolled high blood pressure can harm them and the fetus, but should immediately switch to other drugs. Women contemplating pregnancy were advised to ask their doctors about their options.
``This is a wake-up call. We need to learn more about these drugs to offer better advice to pregnant women," said Dr. J.M. Friedman, a medical geneticist at the University of British Columbia who had no role in the study.
ACE inhibitors, including have been on the market for 25 years, but little research has been done on their effects during early pregnancy with the exception of animal experiments and small studies involving humans. The drugs work by relaxing blood vessels and increasing blood flow to the heart.