Test Predicts Pregnancy Complication
Could Help Prevent Harm to Mom, Child
Sept. 26, 2002 -- Close to 1 in 10 first-time mothers develop a high blood pressure condition called preeclampsia than can lead to pregnancy problems and potentially death in the mom or unborn child. But new research shows that there is a simple way to predict the problem months before it causes symptoms.
Early detection could "eliminate the risks associated with preeclampsia," Ramon C. Hermida, PhD, tells WebMD. The test is actually a combination of old technology with computer-age analysis.
The test would be used for women who are at risk for developing preeclampsia -- women who have already had preeclampsia during a pregnancy, women with a family history of the condition, women who are overweight before becoming pregnant, and women who have diabetes.
It works this way: The woman wears a portable blood pressure monitoring device for 48 hours early in her pregnancy, which records blood pressures at preset intervals. After this time, the blood pressure readings are downloaded into a computer that is programmed to analyze the results. A woman's risk of developing preeclampsia is determined by the number of times her blood pressure varies from normal pregnancy blood pressure.
When it was tested in 403 pregnant women, the device accurately identified 93% of the women who went on to develop preeclampsia. And it was accurate 16 weeks into the pregnancy, five months before women typically develop symptoms.
The test was even more accurate when performed in the third trimester -- identifying 99% of women who would develop preeclampsia late in pregnancy.
Early identification is important, say pregnancy experts, because treatments used when symptoms appear -- usually bed rest and restricting dietary salt -- are often ineffective. Hermida says that preventive strategies such as a diet aimed at minimizing weight gain as well as eliminating salt are likely to work better if started sooner.
The research was presented at a meeting of blood pressure researchers sponsored by the American Heart Association.
"Blood pressure changes predictably during pregnancy. In healthy women, blood pressure declines during the first half of pregnancy and then increases during the second half so that at delivery it is about the same as pre-pregnancy blood pressure," Hermida says. But in women at risk for high blood pressure in pregnancy or preeclampsia, "there is no decrease in blood pressure during the first half of pregnancy, and then there is a dramatic increase in the second half."
In addition, women at risk for blood pressure complications "don't experience a nighttime decline or dip in blood pressure that is seen in healthy women."
John Hall PhD, chairman of the department of physiology at the University of Mississippi Medical Center, says Hermida's results are promising but such blood pressure monitoring is expensive -- adding up to $1,000 to prenatal care. Nonetheless, he says those costs are "minimal compared to the costs associated with care of premature infants or hospital stays for women who have preeclampsia."
Alberto Nasjletti, MD, chairman of the AHA Council for High Blood Pressure Research, tells WebMD that as promising as the test results appear to be, there are other obstacles to its use. He says, for example, that it can be difficult to get women to comply with 24-monitioring of blood pressure. But even if women are willing to undergo testing, it may not be widely available because "it is unlikely that obstetricians have these devices."
But for those who do have the monitoring equipment, there is good news: Hermida says that the test software will be available for free downloads from the Viga University web site later this year.