Low-Dose Aspirin Will Not Prevent Pregnancy Loss

A new study reveals that in general, low-dose aspirin is not beneficial for future pregnancy outcomes in women with prior pregnancy loss.

Researchers at the University at Buffalo (NY, USA) conducted a placebo-controlled trial that included 1,228 women (aged 18-40 years) who were attempting to become pregnant. The participants were stratified by eligibility criteria, with the original stratum restricted to women with one loss at less than 20 weeks' gestation during the previous year, whereas the expanded stratum included women with one to two previous losses, with no restrictions on gestational age or time of loss. The women were block-randomized by treatment center and eligibility stratum.

Preconception-initiated daily low-dose aspirin (81 mg per day) plus folic acid was compared with placebo plus folic acid for up to six menstrual cycles; for women who conceived, study treatment continued until 36 weeks' gestation. Participants, trial staff, and investigators were masked to the assigned treatment. The primary outcome was live birth rate, which was analyzed by intention to treat. In all, 1,078 women completed the study.

The results showed that 58% of those in the low-aspirin group had a live birth, compared with 53% of those in the placebo group. Pregnancy loss occurred in 13% of the women taking low-dose aspirin, and in 12% of the placebo group. Adverse events were similar between the two groups; one adverse reaction, increased vaginal bleeding, was associated with low-dose aspirin, but the bleeding was not associated with pregnancy loss. In all, preconception-initiated low-dose aspirin was not significantly associated with live birth or pregnancy loss in women with one to two previous losses. The study was published early online on April 2, 2014, in the Lancet.

“Preconception use of low-dose aspirin has been found to improve endometrial growth and vascularization in women undergoing in vitro fertilization, and to increase blood flow and reduce inflammation in the reproductive organs,” said lead author Prof. Jean Wactawski-Wende, PhD, of the department of epidemiology and environmental health. “It was hypothesized, therefore, that preconception-initiated, low-dose aspirin might positively affect downstream pregnancy outcomes during that crucial treatment window.”

“One subgroup studied, those with a single documented loss at less than 20 weeks gestation during the previous year, did experience a higher pregnancy rate and live birth rate,” concluded Prof. Wactawski-Wende. “However, our conclusion is that preconception-initiated, low-dose aspirin is not significantly associated with live birth or pregnancy loss in women overall, and the study does not support the general use of low-dose aspirin to decrease the risk of pregnancy loss.”

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