By Dan Vergano, Medical Tribune News Service
Lack of a compound that relaxes arteries can trigger a dangerous
pregnancy complication, report government researchers.
Around 5 percent of all first-time mothers develop preeclampsia,
a condition that includes rapid escalation in blood pressure that
remains until the end of pregnancy. The condition is most common in
the last trimester. Severe cases can lead to eclampsia, which is
marked by convulsions and can cause death.
Children of women with preeclampsia suffer from lower birth
weights, putting them at risk of other ailments.
Despite decades of investigation, no cure for the syndrome has
been discovered. Last year researchers tried using calcium to lower
blood pressure in women suffering from preeclampsia, but the
attempt ended in disappointment.
Use of magnesium sulfate in the late stages of a pregnancy can
have some ameliorative effects on the ailment, said Dr. James L.
Mills, of the National Institute of Child Health and Human
Development (NICHD) in Bethesda, Md., who led the current study.
``But the definitive way to stop it is to deliver the baby,'' he
said.
``Nobody knows what causes preeclampsia,'' said Mills.
Hoping to find some hints about the cause of the ailment, his
research team followed 2,294 women through the course of their
pregnancy. In three-month intervals, the researchers tested the
women's levels of particular blood chemicals suspected of
involvement with preeclampsia.
Over the course of the study, 134 women developed preeclampsia.
Testing revealed these women had significantly lower levels of a
blood chemical called prostacyclin than 139 of their healthy peers,
matched to them in terms of background and medical history.
Prostacyclin levels, which were, on average, 17 percent lower in
the women with preeclampsia, acts to relax the walls of blood
vessels. Mills theorizes that lack of prostacyclin creates an
imbalance between the compounds in the body that act to constrict
and dilate arteries, with the result that blood vessels suffer
excessive tightening during preeclampsia, sending blood pressure
skyward.
``It was a bit of a surprise to find out this was the source of
the hypertension,'' said Mills. Previous studies had implicated
that the culprit was excessive amounts of a blood chemical
responsible for constricting blood vessels. Amounts of such a
``vasoconstrictor'' were higher than normal in the afflicted women,
but not enough to be statistically definitive as a cause of
preeclampsia, said Mills.
The study authors said the variation of prostacyclin levels in
women was too wide to use as an indicator of the condition. They
held out hope that some synthetic version of prostacyclin can be
developed as a treatment.
Another surprise was finding the lowered levels of prostacyclin
appeared relatively early in pregnancy, months before preeclampsia
developed in study participants, according to Mills. The study
appeared in the July 28 issue of the Journal of the American
Medical Association.
``It's exciting news,'' said Dr. Rebecca Jaffe, of Wilmington,
Del., a family physician who has seen many of her patients deal
with preeclampsia. ``It's a medical condition physicians have
struggled with for hundreds of years and never really had a clue
about.''
``Future strategies to deal with preeclampsia should focus on
enhancing prostacyclin production,'' said Dr. Robert N. Taylor of
the University of California San Francisco Medical Center, who has
studied the ailment for 12 years. He said the study confirms that
over the last decade researchers have been looking down a blind
alley in searching for blood chemicals that tighten arteries.
