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NIH Report: Aspirin Shows Mixed Results in Preventing Pregnancy Loss

Only small subgroup of women appears to benefit

Daily low-dose aspirin does not appear to prevent subsequent pregnancy loss among women with a history of one or two prior pregnancy losses, according to researchers at the National Institutes of Health. However, in a smaller group of women who had experienced a single recent pregnancy loss, aspirin increased the likelihood of becoming pregnant and having a live birth.

Many health care providers prescribe low-dose aspirin therapy for women who have had a miscarriage or stillbirth and would like to become pregnant again. However, the effectiveness of this treatment has not been proven, the researchers wrote in The Lancet.

In the largest study of its kind, the authors randomly assigned more than 1,000 women with a history of pregnancy loss to either daily low-dose aspirin or placebo. The women began taking the equivalent of 81 mg of aspirin a day while trying to conceive. The researchers reported that, overall, there was no difference in pregnancy loss rates between the two groups.

“Our results indicate that aspirin is not effective for reducing the chances of pregnancy loss in most cases,” said lead author Enrique Schisterman, PhD. He added, however, that additional research was needed to investigate the finding that women who had experienced a single recent pregnancy loss (before 4.5 months of pregnancy and within the past year) had an increased rate of pregnancy and live birth while on aspirin therapy.

In this subgroup, 78% of those who took aspirin became pregnant, compared with 66% of those who took placebo. For this subset of women, 62% of the aspirin group and 53% of the placebo group gave birth.

The authors hypothesized that aspirin therapy might increase the conception rate by increasing blood flow to the uterus. They called for additional research to determine whether aspirin therapy might be helpful for improving fertility in other subgroups as well, such as women who can’t establish a pregnancy because the embryo fails to implant in the uterus.

The Effects of Aspirin in Gestation and Reproduction (EAGeR) trial was conducted at four university medical centers over a 5-year period. The participants, who were 18 to 40 years of age and predominantly Caucasian, received a daily dose of either aspirin and folic acid or placebo and folic acid.

The women were followed for up to six menstrual cycles while trying to become pregnant and through pregnancy if they became pregnant. Aspirin was stopped at 36 weeks of gestation.

Among all of the participants, 13% who took aspirin and became pregnant subsequently experienced another loss, compared with 12% who received placebo. Ultimately, 58% of women taking aspirin and 53% of the placebo group became pregnant and later gave birth.

Source: NIH; April 1, 2014.

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