Could Low Dose Aspirin Impact Pregnancy Outcomes?

Low-dose aspirin (LDA) therapy prior to conception may improve pregnancy outcomes for women with prior miscarriages, according to the results of a recent study.1

The researchers conducted a per protocol, post-hoc analysis of the Effects of Aspirin on Gestation and Reproduction (EAGeR) trial.2 The aim of this analysis was to account for participant nonadherence, which was not considered in the original trial.

Included were 1227 women between 18 and 40 years old from 1 of 4 university medical centers within the United States. All participants had 1 or 2 prior miscarriages and were attempting pregnancy again.

The women were given either a daily low-dose aspirin (81 milligrams) or placebo while trying to conceive, to be continued through the 36th week of pregnancy. Adherence to the regimen was determined by weighing the pill bottles at regular intervals.

When compared with placebo, for every 100 women in the trial, participants who adhered to LDA for 5 days per week had:

  • 8 more human chorionic gonadotropin-detected pregnancies (95% CI, 4.64 to 10.96 pregnancies)
  • 15 more live births (7.65 to 21.15 births)
  • 6 less pregnancy losses (-12.00 to -0.20)


The results also indicated that a reduction in the estimated effects were observed in those who began LDA therapy post-conception. 

“Per protocol results suggest that preconception use of LDA at least 4 days per week may improve reproductive outcomes for women who have had 1 or 2 pregnancy losses,” the authors concluded. “Increasing adherence to daily LDA seems to be key to improving effectiveness.”


—Leigh Precopio



  1. Naimi AI, Perkins NJ, Sjaarda LA, et al. The effect of preconception-initiated low-dose aspirin on human chorionic gonadotropin-detected pregnancy, pregnancy loss, and live birth: per protocol analysis of a randomized trial. ACP Journals. Published January 26, 2021. Accessed January 26, 2021.
  2. Connell MT, Sjaarda LA, Radin RG, et al. The effects of aspirin in gestation and reproduction (EAGeR) trial: a story of discovery. Semin Reprod Med. 2017;35(04): 344-352. DOI: 10.1055/s-0037-1606384