Study Sheds Light on Possible Causes of Preeclampsia

Finds link to high concentrations of a natural chemical

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HealthDay Reporter

FRIDAY, May 2, 2003 (HealthDayNews) -- Among the most serious of pregnancy complications is a condition known as preeclampsia, a blood pressure-related problem that can develop in the last trimester and threaten the life of both mother and baby.

Now a group of British doctors say they might have a way of predicting who is at risk for preeclampsia, long before symptoms occur.

In a new study appearing in the May 3 issue of The Lancet, doctors from Harris Birthright Centre, Kings College Hospital, London, say problems appear linked to a dysfunction in the cells that line blood vessels -- called endothelial cells -- and a natural chemical known as asymmetric dimethylarginine (ADMA).

"Maternal endothelial function is impaired in women who eventually develop preeclampsia, and it occurs before the development of the clinical syndrome," writes study author Kypros Nicolaides. Women who are at risk for preeclampsia, he says, appear to have high concentrations of ADMA. That chemical seems to contribute to the dysfunction of the cells within blood vessel walls.

"The results of this study may help the development of more accurate tests for the prediction and more effective treatment of preeclampsia," says Nicolaides.

While experts say the study is well done and holds promise, according to obstetrician Dr. Steve Farber it is only one of many promising theories about the cause of preeclampsia.

"With each new study we find another piece of the puzzle, and we have a little better understanding of this complex problem and why it occurs," says Farber, president of the medical staff at Maimonides Medical Center in New York City.

And while he says researchers have focused on the endothelial cells before, it remains to be seen whether ADMA is the missing piece of the puzzle everyone has been hoping to find.

"It would be great if it was, but right now, we just don't know that," Farber says.

Preeclampsia is characterized by a swelling that can occur throughout the body, usually accompanied by a rapid rise in blood pressure. It normally begins late in the third trimester and affects up to 8 percent of all pregnant women, particularly older mothers or those carrying twins or triplets.

In some instances, preeclampsia can develop into the more severe condition known as eclampsia, causing a potentially fatal swelling in the brain. In underdeveloped nations, eclampsia accounts for up to 50,000 maternal deaths a year.

Currently, the only known treatment for preeclampsia is delivery of the baby, which lets blood pressure return to normal and swelling to rapidly decrease. As such, says Farber, doctors and mothers are often forced to play a treacherous waiting game, hoping to give the baby enough time to fully develop within the womb, but still delivering early enough to avoid eclampsia.

The new study involved two groups of 43 pregnant women who had a Doppler ultrasound examination of the uterus (a test that documents blood flow) in their second trimester, while blood tests checked levels of ADMA.

In the first group of 43, the women were shown to have normal uterine arteries and no elevations in ADMA. Subsequently, they all delivered normally with no complications.

In the second group of 43, the Doppler exam revealed impaired blood flow between the uterus and the developing baby. Of this group, 44 percent went on to have normal pregnancies and healthy births. In 33 percent of these women, however, babies developed intrauterine growth restriction, putting them at risk for low birth weight.

The remaining 23 percent developed preeclampsia. Because the Doppler exams revealed abnormal blood flow within the uterine arteries, as well as abnormal blood vessel dilation, researchers suggest arterial dysfunction as a factor in the development of preeclampsia.

More importantly, the women at risk for either preeclampsia or intrauterine growth restriction also had what doctors call a "striking elevation" in the concentration of ADMA in their blood -- which the researchers say may one day serve as a marker for women at risk.

Although Farber says knowing can be important, he adds that right now it does little to change the clinical picture of preeclampsia since delivery still remains the only treatment option.

More information

To learn more about the symptoms of preeclampsia, visit the March of Dimes.To learn more about Doppler ultrasound, check out the American College of Radiology.

SOURCES: Steve Farber, M.D., obstetrician/gynecologist and president, medical staff, Maimonides Medical Center, New York City; May 3, 2003, The Lancet

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