A study in mice suggests that the use of low-dose aspirin to prevent preeclampsia, a dangerous complication of pregnancy, is safe for both the fetus and mom-to-be.

"Based on our results, it seems like low-dose aspirin shouldn't cause any harm to the delivery process and to the normal length of pregnancy. And it shouldn't be harmful to the fetus," said Colin Funk, lead author of the study from Queen's University in Kingston, Canada.

The researchers stress, however, that this study hasn't resolved whether or not aspirin might be effective in reducing risks for preeclampsia, a potentially fatal condition in which maternal blood pressure can suddenly soar, raising risks for stroke, seizures and organ damage.

Preeclampsia affects between 5 percent and 8 percent of all pregnancies, according to the Preeclampsia Foundation. The disorder, whose exact cause is still unknown, is most common in first pregnancies and often starts in the third trimester. Risk factors for the disorder include a prior or family history of preeclampsia, high blood pressure, obesity, diabetes or kidney problems.

In the new study, published online Thursday in the Journal of Clinical Investigation, Funk and his colleagues genetically engineered a strain of mice with reduced levels of the enzyme COX 1. This, in turn, reduced circulating levels of prostaglandin H synthase 1 (PGHS 1), a compound important to clotting.

Similar PGHS 1 reductions also occur during aspirin therapy in humans, so this mouse model should mimic that state, Funk explained.

The researchers then compared the pregnancies of these altered mice to normal mice and to mice that had the COX 1 enzyme-producing gene "knocked out" entirely, leading to drastically lower levels of PGHS 1.

As expected, the "knockout" mice had problems with both pregnancy and delivery, with extended pregnancies that caused some of the mouse babies to die.

However, in the mouse model designed to mimic aspirin use, pregnancies were normal, with mice delivering healthy pups at about 19 days.

with mixed results. He suspects that taking aspirin probably does provide women with a small benefit in reducing preeclampsia, however.

One reason aspirin might help prevent preeclampsia, according to Funk, is that it helps keep the blood from clotting abnormally, which is more likely to happen when blood pressure rises. That's one of the reasons aspirin is often prescribed for older adults to prevent heart attacks.

If the results of this study results hold true in humans, the therapy appears to be safe as well, he said.

Dr. Andrei Rebarber, an obstetrician specializing in high-risk pregnancies at New York University Medical Center in New York City, said the Canadian study "further confirms the mechanism in a mouse model about how low-dose aspirin can be used to prevent preeclampsia without compromising other reproductive functions."

Rebarber noted that many obstetricians currently turn to aspirin to help prevent preeclampsia, because it does appear to offer a slight benefit. It isn't useful, however, in treating women already diagnosed with the condition, he said. That leaves open the question of exactly which patients should receive aspirin as a preventive measure, and when.

More information

To learn more about preeclampsia, visit the Preeclampsia Foundation.

SOURCES: Colin D. Funk, Ph.D., Canada Research Chair in Molecular, Cellular and Physiological Medicine, Queen's University, Kingston, Ontario, Canada; Andrei Rebarber, M.D., associate professor, medicine in maternal and fetal medicine, New York University School of Medicine, and obstetrician/gynecologist, New York University Medical Center, New York City; April 1, 2005 Journal of Clinical Investigation