Is low-dose aspirin therapy to prevent preeclampsia more efficacious in non-obese women or when initiated early in pregnancy?

Abstract

Objective: Late timing of intervention and maternal obesity are potential explanations for the modest effect of aspirin for preeclampsia prevention. We explored whether low-dose aspirin (LDA) is more effective in women at increased risk when initiated before 16 weeks' gestation or given to non-obese women.

Methods: Secondary analysis of a trial to evaluate LDA (60 mg/d) for preeclampsia prevention in high-risk women. Participants were randomized to LDA or placebo between 13 and 26 weeks. We stratified the effect of LDA on preeclampsia by (a) timing of randomization (< 16 or ≥ 16 weeks gestation) and (b) body mass index (BMI) class (non-obese and obese). The Breslow–Day test for homogeneity was used to assess for variations in effect of LDA across gestational age and BMI groups.

Results: Of 2503 women, 461 (18.4%) initiated LDA < 16 weeks. LDA effect was not better when initiated < 16 weeks (RR: 0.93, 95% CI: 0.67–1.31) versus ≥ 16 weeks (RR: 0.90, 95% CI: 0.75–1.08), (p value for interaction = 0.87). Similarly, LDA effect was not better in non-obese (RR: 0.91, 95% CI: 0.7–1.13) versus obese women (RR: 0.89, 95% CI: 0.7–1.13), (p value for interaction = 0.85).

Conclusion: LDA for preeclampsia prevention was not more effective when initiated < 16 weeks or used in non-obese women at risk for preeclampsia. No particular subgroup of women was more or less likely to benefit from LDA therapy.

• Aspirin
• gestational age
• obesity
• preeclampsia
• prevention

Acknowledgements

The authors thank the Eunice Kennedy Shriver National Institute of Child Health and Human Development, the Maternal-Fetal Medicine Units Network and the High Risk Aspirin Trial Protocol Subcommittee for making the database available for the project.

Poster presentation at the Society of Maternal–Fetal Medicine 33rd Annual Meeting, San Francisco, CA, 11–16 February 2013.

Oral presentation at the ACOG 61st Annual Clinical Meeting, New Orleans, LA, 4–8 May 2013.

Declaration of interest

The authors report no declarations of interest.

The contents of this report represent the views of the authors and do not represent the views of the Eunice Kennedy Shriver National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network or the National Institutes of Health.

Supplementary material available online Supplementary Tables 1–4