High Blood Pressure Can Raise Risk Of Birth Defects
October 19, 2011

High Blood Pressure Can Raise Risk Of Birth Defects

Women with high blood pressure (hypertension) during early pregnancy are more likely to have babies born with major birth defects, regardless of their use of prescribed medications to control the condition, according to new research published in the online edition of the British Medical Journal on Oct. 18.

Pregnant women have been warned for years to avoid angiotensin-converting enzyme (ACE) inhibitors during the later stages of pregnancy to avoid the possibility of birth defects. But whether it was safe to take them in the first trimester was not clear.

Three previous small studies found an increased risk of birth defects with pregnant women´s use of blood pressure medications.

However, the findings in the new, much larger study suggest that it is high blood pressure, and not the use of antihypertensive drugs during early pregnancy, as previously believed, that increases the risk of birth defects.

Compared to women without hypertension, those with the condition were more likely to have babies with congenital heart, brain or spinal cord defects regardless of whether they were taking ACE inhibitors, other medications, or nothing at all, according to the study findings.

Dr. De-Kun Li and colleagues from Kaiser Permanente in California studied data of more than 460,000 pregnant women and their babies from 1995 to 2008. Data was also available on which medications had been prescribed and dispensed to these women.

Their analysis showed that women who used ACE inhibitors in their first trimester were more likely to have a baby with some form of birth defect compared with women who did not have hypertension or who had not used any form of antihypertensive medication.

However, a similar elevated risk was found among women who used other antihypertensive drugs and those with hypertension who did not take any antihypertensive medication.

“Our finding suggests that it is likely the underlying hypertension rather than use of antihypertensive drugs in the first trimester that increases the risk of birth defects in offspring,” the researchers concluded.

Professor Allen Mitchell, from Boston University, said in an accompanying editorial that based on the available studies, it would appear reasonable to conclude that first-trimester exposure to ACE inhibitors poses no increased risk of birth defects than any other antihypertensive drug. He believes that, while clinicians must certainly identify and control hypertension, particularly in pregnancy, “we have much to learn about how hypertension can cause birth defects.”

Dr. James Walker, a spokesman for Britain´s Royal College of Obstetricians and Gynecologists, said it was reassuring that blood pressure medications taken in early pregnancy did not increase the risk of birth defects.

He said ACE inhibitors are not commonly prescribed to pregnant women due to past concerns, and that the main concern has been getting them off the drugs as soon as they become pregnant.

“What this study does is reassure us women can stay on the drug until they're pregnant and then stop,” Walker, who was not involved in the study, told the Associated Press. “You never know how long someone is going to take to get pregnant and if they come off a blood pressure drug for too long, it could be bad for them.”

The researchers checked pharmacy databases to see whether women used blood pressure drugs during their pregnancy and also looked at medical records to check for reported birth defects. The team adjusted for potential factors, such as diabetes and obesity.

The US Food and Drug Administration (FDA) advises women to switch from ACE inhibitors to other drugs once they become pregnant, but there are no official warnings against using them in the first trimester of pregnancy.

It remains unclear why high blood pressure in pregnant women could result in birth defects, but the researchers suggest there could be physiological changes in mothers that affect fetal growth.

The study was funded by several groups including the U.S. Agency for Healthcare Research and Quality and the Department of Health and Human Services.


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