ACE inhibitors, a class of medications primarily used to lower blood pressure and/or to preserve kidney function in people with diabetes, already carry an FDA "black box" warning stating that they can cause injury and even death to the developing fetus when used during the second and third trimesters of pregnancy. The warning states that use of ACE inhibitors should be discontinued as soon as possible when pregnancy is detected. According to data from the National Ambulatory Medical Care Survey, in 1995 there were 1,426,220 prescriptions for ACE inhibitors written in physicians' offices for women ages 15 to 44. That number increased to 2,712,510 in 2002 for the same age group.
"These study findings raise a new and potentially important safety concern for a woman who is taking ACE inhibitors before she or her doctor knows that she is pregnant," said AHRQ Director Carolyn M. Clancy, M.D. "Clinicians who treat women of childbearing age and pregnant women should be aware of these new findings and consider whether to use other treatment options to control hypertension or kidney damage from diabetes."
The study was conducted by researchers at the AHRQ-sponsored Vanderbilt University Center for Education and Research on Therapeutics (CERTs) in Nashville. The mission of the CERTs is to conduct research and provide education that will advance the best use of therapeutics (drugs, medical devices, and biological products). The program is administered as a cooperative agreement by AHRQ, in consultation with the FDA.
Researchers, led by William O. Cooper, M.D., M.P.H., of Vanderbilt Children's Hospital, examined data gathered from the Tennessee Medicaid program on 29,507 infants born between 1985 and 2000. Of the total study population, 209 infants were identified by researchers as having been exposed to ACE inhibitors during the first trimester, 202 had comparable exposure to other antihypertensive medications, and 29,096 had no maternal use of antihypertensive drugs.
The researchers found that major congenital malformations identified by vital records and hospital claims were diagnosed in 856, or 2.9 percent of infants, and that 203 infants had more than one malformation. Among infants exposed to ACE inhibitors in the first trimester, the proportion born with major congenital malformations was 7.1 percent, compared with 1.7 percent among infants exposed to other antihypertensive medications. The rate of major congenital malformations in the general population is about 3 percent—or 3 infants out of every 100 pregnancies.
The chances of a major congenital malformation among infants exposed to ACE inhibitors during the first trimester were 2.71 times higher than in infants whose mothers did not use any hypertension medications. The increased overall risk seen with ACE inhibitors was due primarily to higher risks for cardiovascular and central nervous system malformations, including atrial septal defects (hole in the wall that separates the two upper chambers of the heart), patent ductus arteriosus (an open blood vessel that causes blood to flow into the baby's lungs), hydrocephalus, and spina bifida. The risk for all other types of malformations, including those of the musculoskeletal, gastrointestinal and genital systems, was not significantly increased by first-trimester exposure to ACE inhibitors, the researchers found.
"This study raises the important issue of a woman and her physician being aware of potential risks of medications that she might be taking before she becomes pregnant," Dr. Cooper said. "While we believe the increased risk that we found in our study represents a true increase, further studies are needed to confirm these findings and to assess the risks of specific drugs and durations of exposure."
AHRQ is sponsoring followup studies on the effects of drug exposures during pregnancy. The research on ACE inhibitors and other related classes of medications, such as the angiotensin receptor blockers or ARBs, will be conducted through its DEcIDE research network, in consultation with scientists from the FDA.
For more information, please contact AHRQ Public Affairs: (301) 427-1855 or (301) 427-1245.