MONDAY, Nov. 5, 2001 (HealthDayNews) -- If you're pregnant, a daily dose of aspirin may save your life. A new study shows that pregnant women at high risk for preeclampsia -- a dangerous form of high blood pressure -- could reduce those risks by taking a low-dose aspirin every day.
"We knew from [previous studies] that a uterine Doppler test would predict women at high risk for preeclampsia, [and] our current review shows that aspirin has substantial benefit in these high-risk women," says Aravinthan Coomarasamy, study author and researcher at Birmingham Women's Hospital in Birmingham, England.
A Doppler exam is a type of ultrasound that uses harmless radio waves to measure the speed at which blood flows through the vessels. If the test indicates a blockage or other problem that could hamper blood flow to the uterus, many doctors believe the risk for preeclampsia increases. And it is for these women that experts say the aspirin therapy is promising.
"Very roughly, it halves the risk of preeclampsia in women who have an abnormal uterine Doppler test," says Coomarasamy. Currently, the American College of Obstetrics and Gynecology suggests, up to 8 percent of all pregnant women may be at risk for preeclampsia.
The idea that aspirin may help is not new. In fact, this particular study was a scientific review of more than 300 previous studies that examined the role of aspirin in the prevention of preeclampsia.
Although much of the research yielded conflicting results, the authors believed it was the study designs, not the treatment, that was responsible for the ambiguities.
"Too many women in the [previous analyses] were at very small risks of preeclampsia, [so] basically these women would not have benefited -- or benefited only a little -- from aspirin," says Coomarasamy.
Including these low-risk women with high-risk women diluted the results, which is why it wasn't clear what aspirin's benefits were for those studies, say the authors.
Once the analysis was limited to only those women at high risk for preeclampsia, and specifically those who were diagnostically proven at risk via the Doppler ultrasound, an aspirin a day was clearly shown to have protective effects.
"The study was very well done; the authors seem to have performed a thorough search for all relevant studies, and they have evaluated each possibly relevant study for its strengths and weaknesses," says Dr. Fergal Malone, director of the Columbia Perinatal Center at Columbia Presbyterian Medical Center in New York City.
However, he adds that, "One should be careful about making large sweeping policy decisions on the basis of meta-analyses alone -- they may help answer a question, but can sometimes show significant results where none truly exist," says Malone. Any flaws in the original studies, he says, will affect the overall results of the new analysis.
The authors went back as far as 1966 to retrieve 332 studies on preeclampsia and aspirin for review. After eliminating all those that were too broadly based or otherwise included too many low-risk or no-risk women, the authors settled on only five studies, which met their rigorous criteria. All were published after 1990, and all included women at very high risk for preeclampsia as determined by a Doppler ultrasound exam.
After analyzing the collective data on more than 1,300 women, the authors concluded that when Doppler ultrasound revealed a uterine abnormality, aspirin did "reduce the risk of preeclampsia substantially," says Coomarasamy. The authors say they don't know why or how the aspirin works.
The study was published in the November issue of Obstetrics and Gynecology.
What To Do
There is no existing treatment for preeclampsia other than giving birth. Although aspirin may help prevent problems, Malone points out that it's not a treatment -- and that it must be taken before the 24th week of pregnancy in order to be preventative.
He also cautions that daily aspirin use may slightly increase the risk of placental abruption -- a separation of the pregnancy sac from the uterus, which can put a baby's life at risk. Coomarasamy , however, believes this has never been fully proven, and says the therapy is safe.
"There is generally no obstetric contraindication for aspirin," says Coomarasamy, who does concede that women should consult with their doctor before using aspirin daily during pregnancy.
One final note: Since previous studies have failed to show interventions for preeclampsia were effective, a diagnostic Doppler ultrasound -- popular in England, where this study was done -- is rarely performed in the United States before the 20th week of pregnancy.
According to Malone, the test is unlikely to catch on unless other studies validate that interventions for preeclampsia are effective, thereby increasing the importance of diagnosing those at risk.
To learn more about high blood pressure and pregnancy, visit the Preeclampsia Foundation.
For more information on screening for preeclampsia, click here.
Want to learn more about Doppler ultrasound? Click here.
