Birth defects may be linked to high blood pressure, not use of ACE inhibitors in early pregnancy

Research Activities, December 2011, No. 376

Women who take angiotensin-converting enzyme (ACE) inhibitors to treat high blood pressure in the first trimester of their pregnancies are at no greater risk of having babies with birth defects than are women who take other types of high blood pressure medication or who take no blood pressure drugs, according to a new study from the Agency for Healthcare Research and Quality (AHRQ). The study suggests that the underlying high blood pressure itself may increase the risk of birth defects, rather than blood pressure medications taken during the first trimester of pregnancy.

ACE inhibitors are among the most widely prescribed drugs used to treat high blood pressure, particularly for people who also have diabetes. ACE inhibitors are known to raise the rate of birth defects in the second and third trimesters of pregnancy, and one earlier study reported a link between the use of ACE inhibitors and birth defects in the first trimester of pregnancy. But the new AHRQ report, based on a study of a larger population, did not find a unique link between first-trimester ACE inhibitor use and birth defects. Results of the study, prepared for AHRQ's Effective Health Care Program by the HMO Research Network, a member of AHRQ's Developing Evidence to Improve Decisions about Effectiveness (DEcIDE) Network, were published in the October 18 issue of the British Medical Journal.

"Some women of child-bearing age have high blood pressure, and about half of them will get pregnant while taking one or more medications to treat it," said AHRQ director Carolyn M. Clancy, M.D. "This report should lead to more informed discussions by women, in consultation with their doctors, about the best way to manage their high blood pressure, particularly if they become pregnant. ACE inhibitors are also used to treat heart failure and to protect some people from diabetes complications. Yet because they work by inhibiting an enzyme in the kidney, physicians caution patients about taking them in the second and third trimesters of pregnancy, a crucial period of development for the unborn baby.

ACE inhibitors carry a "black box" warning from the Food and Drug Administration—that agency's strongest warning—against their use in the second and third trimesters of pregnancy. However, the new AHRQ study, which examined more than 465,000 babies born over 13 years in the Kaiser Permanente Northern California region, found no correlation between ACE inhibitor use during the first month of pregnancy and birth defects. The new report found that birth defects occurred at the same rate among all women with high blood pressure, regardless of whether they took ACE inhibitors, other drugs to treat high blood pressure, or no blood pressure drugs.

While the AHRQ study did not conclude that high blood pressure is explicitly to blame for increased birth defects, researchers said that the findings suggest that underlying high blood pressure likely results in increased birth defects. Thus, taking steps to reduce blood pressure before pregnancy—including losing weight and reducing sodium intake—may reduce the risk of birth defects.

The study, "Maternal Exposure to Angiotensin Converting Enzyme Inhibitors in the First Trimester and Risk of Malformations in Offspring: A Retrospective Cohort Study," is the latest study from AHRQ's Effective Health Care Program. More information about the program can be found at the Effective Health Care Program Web site.

Current as of December 2011
Internet Citation: Birth defects may be linked to high blood pressure, not use of ACE inhibitors in early pregnancy: Research Activities, December 2011, No. 376. December 2011. Agency for Healthcare Research and Quality, Rockville, MD. http://www.ahrq.gov/news/newsletters/research-activities/dec11/1211RA28.html