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First trimester use of ACE inhibitors implicated in birth defects

June 08, 2006

The Food and Drug Administration is examining study data from Vanderbilt University Medical Center researchers, published this week in the New England Journal of Medicine, to determine if new warnings should be placed on common blood pressure medications indicating an increased risk of birth defects for babies whose mothers take these medications during the first trimester of pregnancy.

The study, led by William Cooper, M.D., M.P.H., associate professor of Pediatrics at the Monroe Carell Jr. Children's Hospital at Vanderbilt, found infants born to mothers who took angiotensin converting enzyme inhibitors (ACE inhibitors) during the first trimester of pregnancy had an increased risk of major birth defects, compared with infants whose mothers did not take these medications.

Out of 29,507 infants whose TennCare records were examined for the study, 209 were exposed to ACE inhibitors in the first trimester only. When those babies were compared to the rest of the population, including babies exposed to other types of antihypertensive medications, they had more than double the risk of major birth defects, especially of the heart and central nervous system.

Cooper is first author on the study, which includes co-authors from the Departments of Pediatrics, Preventive Medicine and Biostatistics.

"We knew ACE inhibitors were a possible cause of adverse fetal outcomes when exposure occurred later in pregnancy, but it has not been well studied in the first trimester," Cooper said. "We were very surprised that even after controlling for other risk factors, the TennCare records we examined showed a clear increase in a broad range of birth defects following first-trimester-only exposures."

This research is important because of an increase in the number of women of childbearing age who develop high blood pressure and are prescribed ACE inhibitors. These drugs already carry a warning that they may cause injury and even death to the developing fetus when used during the second and third trimesters of pregnancy. The warning states that a woman should discontinue use of ACE inhibitors as soon as possible once she becomes pregnant.

Cooper and his co-authors performed this research within the Child and Adolescent Health Research Unit at the Children's Hospital. The study was jointly funded by the FDA and Vanderbilt's Center for Education and Research on Therapeutics, which is funded through the Department of Health and Human Services' Agency for Healthcare Research and Quality.

Results are published in the June 8 issue of the New England Journal of Medicine.

Vanderbilt University Medical Center