To evaluate the effect of low dose aspirin (LDA) initiated preconceptionally on the risk of preterm birth (PTB, live birth at <37 weeks’ gestation).
The EAGeR trial was a multi-center, randomized, double-blind, placebo-controlled trial of 1,228 US women conducted in 2006-2012. Women 18 to 40 years old with a history of pregnancy loss trying to conceive were eligible for the study. Participants were stratified based on eligibility criteria: 1) original: women with 1 pregnancy loss at <20 weeks’ gestation during the past 12 months; 2) expanded: women with 1-2 prior losses, regardless of gestational length or recency. Participants were block-randomized by study center and stratum to either daily LDA (81 mg, n=615) or an identical looking placebo (n=613). Participants were followed for 6 menstrual cycles or through gestation if they became pregnant. Pregnancy end date was assessed by post-partum interview and medical record review. Gestational age was determined by an ultrasound conducted in early pregnancy for 98% of pregnancies conceived during the study.
Approximately 88% (n=1078) of randomized participants completed the study. In the intent-to-treat analysis, PTB risks were: overall, 4.1% (22/535 LDA) and 5.7% (31/543 placebo) (p=0.22); in the original eligibility stratum, 2.9% (7/242 LDA) and 6.4% (16/250 placebo) (p=0.06); and in the expanded stratum, 5.1% (15/293 LDA) and 5.1% (15/293 placebo) (p=1.0). After restriction to confirmed pregnancies, the PTB risks were 5.9% (22/374 LDA) and 9.0% (31/346 placebo) (p=0.12). Using inverse probability weighting to account for different rates of conception by intervention arm, the PTB risks were 3.8% (LDA) and 5.7% (placebo) (p=0.15).
Preconception LDA was not significantly associated with the risk of PTB. However, we observed a trend towards lower PTB in the LDA study arm within the confirmed pregnancies and the original eligibility stratum, which warrants further investigation.
© 2014 Published by Elsevier Inc.