Daily Low-Dose Aspirin Can Boost Chances of Successful Pregnancy

For some women who are trying to get pregnant, taking a low dose of aspirin daily may boost their chances of having a baby, according to a new analysis.

The analysis, which looked at women who'd had a prior pregnancy loss and taken part in an earlier study, found that women who benefited from the aspirin regimen had high blood levels of C-reactive protein (CRP), a marker of inflammation in the body. Among these women, those who took a daily aspirin were 31 percent more likely to become pregnant, and 35 percent more likely to carry a pregnancy to term, than those who took a placebo.

However, it's too soon to officially recommend daily aspirin to prevent pregnancy loss, the researchers said.

Prior to this report, researchers knew that inflammation in the body could contribute to reproductive problems. For example, women with pelvic inflammatory disease or polycystic ovary syndrome — two conditions that involve inflammation — are at increased risk for infertility. But few studies have examined whether lowering levels of inflammation in a woman's body would affect her chances of successfully becoming pregnant and giving birth.

In the new analysis, the researchers analyzed information from more than 1,200 U.S. women ages 18 to 40 who had previously experienced a miscarriage or stillbirth. The women were randomly assigned to take either a low dose of daily aspirin (81 milligrams) — which is thought to counteract inflammation — or a placebo, for six menstrual cycles while they were trying to become pregnant. If the women became pregnant, they continued taking the pills until 36 weeks of pregnancy. (A full-term pregnancy is 39 to 40 weeks.)

Then, the researchers divided the women into three groups: those with low, medium and high CRP levels.

Overall, 55 percent of the women in the study became pregnant and gave birth.

Among the women with high CRP levels, those who took a daily aspirin had a birth rate of 59 percent, compared with just 44 percent among those who took the placebo. Taking daily aspirin also lowered CRP levels in the women with the highest CRP levels.

Women with low or medium CRP levels had about the same birth rate, regardless of whether they took aspirin or a placebo, the researchers found.

In an earlier analysis of this same study, published in 2014, researchers did not find a link between taking aspirin and a reduced risk of pregnancy loss. But for that analysis, the researchers did not look at the level of inflammation in the women's bodies.

The new findings suggest that "inflammation may significantly harm women's ability to become pregnant," and that taking aspirin prior to conception may reduce this risk, the researchers said.

In the future, doctors might consider using a screening test for CRP levels to determine whether a woman may benefit from aspirin treatment before and during pregnancy, the researchers said. However, future studies would be needed to examine this, and to determine exactly what the cutoff would be for "high" CRP levels, they said.

Taking high doses of aspirin (more than 100 milligrams a day) during pregnancy may increase the risk of pregnancy loss, congenital defects and complications with the fetuses' heart, according to the Mayo Clinic. Women should speak with their doctor about taking pain medication during pregnancy.

The anaysis, conducted by researchers at the Eunice Kennedy Shriver National Institute of Child Health and Human Development, was published online Feb. 3 in the Journal of Clinical Endocrinology and Metabolism.

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