Is High Blood Pressure Linked to Birth Defects?

November 12, 2012

Is High Blood Pressure Linked to Birth Defects?

Birth Defects more Common in Pregnant Women With High Blood Pressure

High blood pressure during pregnancy is in the spotlight again due to a recently published report. The report which is published in the journal BMJ challenges previous research which has indicated that blood pressure medications known as ACE inhibitors increase the risk of an abnormal baby if taken during the first trimester of pregnancy. According to this new report there is no increased risk of birth defects if ACE inhibitors are used during the first trimester.

It is generally acknowledged that using ACE inhibitors in the second and third trimesters does increase the risk of birth defects. Because of this the U.S. FDA insists that ACE inhibitors carry a ‘black box’ warning, the most serious classification used by the FDA. The warning must explain the risks of an association with birth defects.

The new report states that if ACE inhibitors are used by women with high blood pressure during the first trimester of their pregnancy then their risk of having a child with birth defects is no greater than that of pregnant women using other types of hypertension medications, or even no medications at all.

Previous research centers on a 2006 report which found that when ACE inhibitors were taken during the first trimester of pregnancy, and no other medication for hypertension was taken, then the risk of birth defects increased. A common form of defect included heart malformations.

It is suspected in the recent report that it may be the high blood pressure which increases the risks for birth defects and not the drugs being used to treat the condition. The researchers say that pregnant women with high blood pressure have an increased risk of the baby being born with birth defects. They also say that the most common defects are heart malformations and defects with the neural tubes.

The study was large scale with the researchers examining data held on 465,754 mothers and their babies over thirteen years from 1995 to 2008. Any medication that the mothers were taking was included in this information. It was found that it was not only women taking blood pressure medication that had an increased risk of having a baby with a defect, women with untreated hypertension also had an increased risk of having a baby with some form of defect.

The reason why untreated high blood pressure can increase the risk of birth defects was not investigated in this study but the researchers postulate that it may affect the blood flow to the fetus.

Encouraging News for Women with Unplanned Pregnancies

Howard Strassner, MD is the chairman of the department of obstetrics and gynecology at Rush University Medical Center in Chicago and he feels that this is good news for women who fell pregnant while they were taking ACE inhibitors. Because about 50% of all pregnancies are unplanned, it is possible to be taking ACE inhibitors before women know that they are pregnant. Especially as ACE inhibitors are one of the most commonly prescribed treatments to lower blood pressure.

Eva K. Pressman, MD is professor of obstetrics and gynecology and director of maternal and fetal medicine at the University of Rochester and she points out that it is always a good idea to talk to your health professional if you have any underlying conditions and are considering having a baby. She adds, “In the ideal world, they would change medications first, but if they are on an ACE inhibitor and become pregnant, they can switch to another by second trimester”. She then explains the importance of treating hypertension during pregnancy by saying,” Women who have high blood pressure during pregnancy are at risk for complications including preterm birth and preeclampsia, a potentially fatal pregnancy-related condition.”

Of the study, Allen A. Mitchell, MD says, “The data would suggest that there may be a modest increase in the risk of certain birth defects among women with hypertension, whether it is treated or not”. Mitchell is director of the Slone Epidemiology Center at Boston University Schools of Public Health & Medicine, and he wrote an editorial supplement for the new study.

He also says that anyone with high blood pressure should adopt a healthier lifestyle with a better diet and more exercise. But he adds that women can take some reassurance from this report which does seem to imply that blood pressure medications do not increase the risk of birth defects during the early stage of pregnancy. He finishes on a cautious note by saying, “At the same time, it is important for the health of both mother and infant to control maternal hypertension, since the complications of this condition can be quite serious to both”.

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