Preconception low dose aspirin and time to pregnancy: findings from the effects of aspirin in gestation and reproduction randomized trial

The objective was to determine the effect of preconception-initiated daily low-dose aspirin (LDA; 81 mg/day) treatment on time to pregnancy in women with a history of pregnancy loss.

This was a multicenter, block-randomized, double-blind, placebo-controlled trial. Participants were block-randomized by center and eligibility stratum.

The study was conducted at four U.S.A. medical centers (2007-2012).

Participants women aged 18-40 years actively attempting pregnancy, stratified by eligibility criteria: the "original" stratum, women with one loss <20 weeks' gestation during the previous year; and the "expanded" stratum, women with one or two previous losses of any gestational age regardless of time since loss.

Daily LDA was compared with matching placebo for up to six menstrual cycles of attempting pregnancy.

Time to hCG detected pregnancy and clinically confirmed pregnancy, analyzed by intention-to-treat, was measured.

Of the 1228 women randomly assigned to LDA (n = 615) or placebo (n = 613), 410 (67%) women receiving LDA achieved pregnancy compared to 382 (63%) receiving placebo, corresponding to a fecundability odds ratio (FOR) of 1.14 (95% CI: 0.97, 1.33). Among women in the original stratum (n = 541), LDA was associated with increased fecundability compared to placebo (For: 1.28; 95%CI: 1.02, 1.62).

Preconception-initiated LDA treatment resulted in a nonsignificant increase in fecundability of 14% in women with a history of 1-2 pregnancy losses, and a significant increase of 28% in women with a history of only one pregnancy loss of <20 weeks' gestation in the preceding year. Preconception-initiated LDA may increase fecundability in certain women with a recent early pregnancy loss.