Oct. 27, 2000 (Washington) -- The cause of the dangerous rise in the blood pressure of pregnant women has long been a medical mystery. But researchers from Wake Forest University School of Medicine in Winston-Salem, North Carolina and another team from Santiago, Chile, have found what appears to be an important clue to the cause of the condition called preeclampsia.
It is not clear what brings on the episodes of high blood pressure, but preeclampsia tends to run in families and may have a genetic cause, say researchers.
About 6% of pregnant women in the U.S. develop preeclampsia. While the disease can be serious and sometimes fatal, it more commonly forces women to be admitted to the hospital for bedrest and monitoring. This helps their doctors determine the best time to deliver the baby, which is the only known cure for the disease.
Two different studies suggest that the hormone angiotensin-(1-7) may be critical in controlling this blood pressure, swelling, and protein in the urine that can develop during the last weeks of pregnancy. Normally, angiotensin-(1-7) operates as a dilator to keep blood vessels open. However, in women with preeclampsia, the hormone level goes down rather than up, as it does in women with normal pregnancies. That can result in narrowing of the blood vessels and a rise in blood pressure.
The Wake Forest study included 15 women with preeclampsia, 15 normal pregnant women, and 15 nonpregnant women. Studying blood samples, the researchers looked at several substances involved in regulating blood pressure including angiotensin-(1-7). Typically, all of them would be expected to increase during pregnancy. However, the patients with preeclampsia all had lower levels than the normal women.
Apparently this is the first time that angiotensin-(1-7) levels have been measured in pregnant women, according to the lead researcher K. Bridget Brosnihan, PhD, a professor at Wake Forest. She tells WebMD the finding may lead to new screening tests as well as treatment.
While this is a small study, Brosnihan says she is hoping to hear soon from the NIH about a possible larger project. The idea would be to get a relatively large group of pregnant women and follow them throughout pregnancy, as opposed to measuring "one point in time."
Brosnihan also says it might be possible to use the angiotensin-(1-7) as a treatment if it appeared the level of the hormone was dropping rapidly. In a drug form, it is not likely the hormone would have serious side effects, says Brosnihan.
Meanwhile, the Chilean research at Pontificia Universidad Catolica School of Medicine looked at the levels of angiotensin-(1-7) in the urine of two groups of women. They noted a rise in angiotensin-(1-7) starting at 12-13 weeks of pregnancy and reaching peak levels reached around 33-35 weeks. "The levels in the urine are phenomenal, and they increase over the whole course of pregnancy, reaching levels that are 35- to 40-fold higher than the nonpregnant women," says Brosnihan.
She says that is "substantial evidence" that having the hormone in abundant amounts can keep blood pressure in check.