Aspirin may block pregnancy hypertension.

Aspirin, that old standby of the home medicine cabinet, recently proved its worth in reducing the risk of heart attack and some types of stroke. Now, statisticians suggest that very low daily doses of aspirin help protect pregnant women from a risky type of high blood pressure.

Pregnancy-induced hypertension (PIH) strikes up to 15 percent of all pregnant women in the United States. Some develop preeclampsia, in which blood pressure rises, usually during late pregnancy, with symptoms such as headaches, blurred vision and swollen ankles. Preclampsia can progress to eclampsia, which causes seizures, coma and sometimes the death of the mother and fetus.

Some researchers have speculated that PIH results from overproduction of thromboxane [A.sub.2], a fatty-acid derivative that constricts blood vessels -- including those in the placenta, which deliver nourishing blood to the fetus. To test the theory, several teams have focused on aspirin treatment, since aspirin inhibits the body's synthesis of thromboxane [A.sub.2]. However, the preliminary trials conducted so far have provided no clear-cut picture of the drug's potential for preventing PIH.

Now, two researchers have taken another look at those data, this time using a powerful statistical method, called meta-analysis, that combines data from several different studies and thus improves the researchers' ability to detect treatment effects.

At Case Western Reserve School of Medicine in Cleveland, Thomas F. Imperiale and Alice Stollenwerk Petrulis analyzed data from six small clinical trials with low statistical power. The studies, conducted in the 1980s, had yielded results ranging from no aspirin benefit to marked reductions in PIH risk. All 394 pregnant participants had a past history of PIH or other risk factors for the condition. About half received small daily doses of aspirin (60 to 150 milligrams), usually beginning in the second trimester. Each trial included a control group, but some control groups received daily placebo tablets, while others received no placebo.

For a clearer estimate of aspirin's effects, the Cleveland researchers pooled the data from all six studies. In comparing treated women with controls, they discovered that the low aspirin doses reduced the chances of developing PIH by 65 percent -- a highly significant risk reduction, according to the team's report in the July 10 JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION.

Aspirin also reduced the chances of bearing a severely low-birthweight baby -- a threat that often accompanies PIH. Such tiny babies commonly suffer multiple health problems.

Imperiale and Petrulis found no adverse effects associated with aspirin treatment. However, they note that the treated volunteers took only 1 to 1 1/2 child-size aspirin tablets daily. In some individuals, the higher dose in an adult-size tablet could trigger hemorrhaging and other problems, Imperiale warns. The researchers advise pregnant women to consult their obstetricians before considering daily aspirin therapy, even at low doses.

While the new report supports the theory linking aspirin, PIH and thromboxane [A.sub.2], obstetrician John T. Repke points out that researchers have yet to establish aspirin's safety and efficacy against PIH in a large clinical study of pregnant women.

Repke, of the Johns Hopkins University School of Medicine in Baltimore, says his own preliminary trials hinted that calcium supplements may help prevent PIH.

That theory gains backing from a Canadian study reported in the June 15 AMERICAN JOURNAL OF EPIDEMIOLOGY. The new work -- an epidemiologic study led by Sylvie Marcoux of Laval University in Ste. Foy, Quebec -- suggests that a calcium-rich diet, especially during the first and second trimesters, may reduce the risk of developing a hypertensive disorder during pregnancy.