THURSDAY, April 4 (HealthDayNews) -- A simple blood test may soon predict which pregnant women will develop a life-threatening form of high blood pressure known as preeclampsia -- and it could be done early enough to give potentially life-saving care.
Reporting in today's Journal of Clinical Endocrinology and Metabolism, researchers from Massachusetts General Hospital say the key appears to lie in decreased blood levels of SHBG (sex hormone binding globulin), a protein also associated with a pre-diabetic condition known as insulin resistance.
"Women who had below normal levels of SHBG in their first trimester of pregnancy went on to develop preeclampsia far more frequently than those who had normal levels, indicating to us that SHBG could act as a marker, helping to identify those at greatest risk long before symptoms occur," says study author Dr. Myles Wolf, a researcher at Massachusetts General.
Other doctors involved in preeclampsia research elsewhere, however, are not so sure the finding will hold up in larger studies.
"It's much too early to tell," says Dr. Edmund Funai, a researcher and director of obstetrics and gynecology at Bellevue Hospital in New York City. "At this point, I wouldn't suggest that every woman run out and get a blood test for SHBG. We need much more information before we can make any general recommendations."
Preeclampsia, also known as "toxemia," is characterized by a sudden and dangerous rise in blood pressure, combined with other metabolic abnormalities. Symptoms, which usually begin somewhere in the third trimester, can affect 5 percent to 7 percent of all pregnancies -- or 200,000 American women. Sometimes preeclampsia can progress to the more serious form, known as eclampsia, which is marked by violent seizures and kidney or liver failure. Babies of mothers with either condition are usually delivered by emergency C-section , and are often premature.
Although no one is certain what causes preeclampsia, Wolf and his team suspect it may be linked to insulin resistance, a problem that interferes with the body's ability to clear sugar from the blood and is often a precursor to Type II diabetes.
Because insulin resistance is associated with obesity, and obesity is already a known risk factor for preeclampsia, Wolf believed there could possibly be a direct connection from the insulin problem to the pregnancy complication. One of the ways to find that out was to measure the levels of SHBG, which are altered by insulin resistance, so that's what the study set out to do.
First, the researchers accessed medical records from participants in the Massachusetts General Hospital Obstetrical Maternal study, a large project involving 4,500 pregnant women who had given blood samples in their first trimester. All the samples had been tested, among other things, for levels of SHBG.
Wolf's group then identified 45 women who developed preeclampsia, and compared the results of their SHBG blood levels to 90 randomly selected women who had a normal pregnancy.
They found the women who went on to develop preeclampsia were far more likely to also have low blood levels of SHBG, the marker for insulin resistance. The surprising factor, however, was that thin women were as likely to have the low levels as heavy women -- and they were just as likely to develop preeclampsia.
"This told us that with or without obesity, insulin resistance, on its own, could play a role in preeclampsia," Wolf says.
Wolf now believes testing levels of SHBG as early as the first trimester would alert doctors to which women need special care, and doing so early, enough could make a difference in the outcome of the pregnancy.
"There are some treatments for preeclampsia that may actually work if they could be started early enough, before symptoms develop," Wolf says. "This test could help identify which women might benefit from that early treatment."
Funai, however, remains unconvinced of the need for SHBG testing until more evidence is in.
"This study is very interesting, but in order for this finding to really have impact, it would have to be duplicated in a much larger group of women, and it would be necessary to prove that the insulin resistance alone was the underlying factor, and right now that is not clear," he says.
Additionally, Funai says, preeclampsia is far more likely to be a multi-faceted problem, with no one single cause for every woman.
Wolf agrees: " I think there is going to be more than one factor involved. But right now, insulin resistance appears to be one of those factors."
Other risk factors for preeclampsia include pre-pregnancy high blood pressure, diabetes and gestational diabetes, which develops during pregnancy. However, treatments for any of these disorders don't work for preeclampsia. Risks can also be higher in women carrying more than one baby, in mothers over the age of 35, and in those who experienced preeclampsia in a previous pregnancy.
What To Do
Interested in learning more about preeclampsia? Visit The Preeclampsia Foundation.
In addition, to learn more about insulin resistance, check out The American Family Physician.
