Aspirin Protects Pregnant Women With Hypertension

THURSDAY, Sept. 26, 2002 (HealthDayNews) -- One of the world's most versatile painkillers, now more than 100 years old, may have yet another use.

A low dose of aspirin prevented premature labor in a small study of pregnant women at risk for high blood pressure. The findings were presented today at the American Heart Association's 56th annual High Blood Pressure Research Conference in Orlando, Fla.

The aspirin therapy only worked, however, if given at night and when started before the 16th week of pregnancy. When those conditions were met, women showed reductions in gestational high blood pressure and in complications related to preeclampsia.

Preeclampsia includes swelling, elevated blood pressure and protein in the urine during pregnancy.

The women receiving the aspirin therapy also gave birth to babies an average of nine ounces heavier than women who took a placebo or who took aspirin at different times of the day.

Remarkably, not one delivered prematurely.

"Aspirin had no effect on blood pressure when taken by hypertensives (those with high blood pressure) in the morning. However, blood pressure was significantly reduced when they took it at night," says Ramon C. Hermida, lead author of the study and a professor at the University of Vigo in Vigo, Spain.

Although other studies have looked at aspirin and pre-term labor, this was the first to show that timing matters. This study also used a higher dose of aspirin than previous studies and started the therapy earlier in the pregnancy.

"This would be a remarkable finding if it bears out to be true," says Dr. Ralph Dauterive, head of obstetrics/gynecology at the Ochsner Clinic Foundation in New Orleans.

"Aspirin has been tossed around for years, but there have been no good studies that aspirin decreases the incidence of premature labor. The data has been confusing, and no conclusions have been drawn from them," Dauterive says.

According to the National Heart, Lung, and Blood Institute (NHLBI), 6 percent to 8 percent of all pregnancies in the United States include high blood pressure problems. About 70 percent are first-time pregnancies.

Many women with high blood pressure have few or no problems during pregnancy. In some cases, however, the condition can cause early delivery and low birthweight. In more extreme examples, women can develop preeclampsia, which can affect the placenta as well as the mother's kidney, liver and brain. In some cases, it can be fatal to both mother and baby.

Right now, much of the treatment for these conditions involves watching and waiting. "In obstetrics there's a lot of waiting," Dauterive says. "We wait for the disaster, and then we treat it and get it out of the way. The best thing we do is deliver the baby."

In the new study, the researchers randomly assigned 341 pregnant women into six groups. All the women were at high risk for blood pressure problems because they were overweight, had family or personal histories of gestational high blood pressure or preeclampsia, or had had previous miscarriages.

The groups varied, depending on whether they got 100 milligrams of aspirin or a placebo and at what time of day. All treatment started between 12 and 16 weeks of pregnancy.

"Their approach was to give more than in previous studies and at different times," Dauterive points out. "They went in to answer two questions: Do you need to give more of the drug, and is it the timing which is important? According to the data, the answers were 'yes' and 'yes.'"

In the placebo group, the incidence of preeclampsia was 14.3 percent versus only 1.7 percent in the aspirin group. Almost one-third (30.4 percent) of women in the placebo group experienced gestational hypertension (high blood pressure), compared with only 6.8 percent in the aspirin group. While 17.9 percent of women in the placebo group experienced pre-term labor, none of the women taking aspirin had their babies early.

It's not clear why the aspirin had this effect. Some experts believe the drug could affect prostaglandin synthesis, which, in turn, affects uterine contractions.

"We are digging into why it works," Hermida says. "It may not be one single mechanism but a combination of several different factors, all of which could be relevant."

Scientists already knew that aspirin lasts longer when taken at night because the gastrointestinal system is at relative rest during those hours. The drug's effect on nitric oxide, which is involved in blood pressure regulation, may also be involved.

The new study was a small one and the 0 percent prematurity rate was extremely surprising, Dautervive says.

"It's almost an unreal number, but it may be because they only had 50 patients in the group," he says. "They probably need to let this run a little longer, and get some more numbers and see if the numbers hold out. Then the question is: Does this work in the general population? Should we give aspirin to all first pregnancy patients because that's where the biggest risk of preeclampsia lies."

For the time being, if you're pregnant, don't take aspirin -- or any other medication -- without talking to your physician first. High doses of aspirin can increase the risk of bleeding during delivery.

What To Do

For information on high blood pressure in pregnancy and preeclampsia, visit the National Heart, Lung, and Blood Institute, the Preeclampsia Foundation, or the National Library of Medicine.