Early initiation of low-dose aspirin before 12 weeks improves pregnancy outcomes in women with moderate-risk factors for preeclampsia.

BACKGROUND

Preeclampsia is thought to originate from abnormal placentation during early pregnancy. Low-dose aspirin (LDA) reduces the risk of preeclampsia, but most clinical guidelines recommend initiation at 12 weeks of gestation because evidence supporting earlier use remains limited.

OBJECTIVE

To evaluate whether initiation of LDA before 12 weeks of gestation improves maternal and neonatal outcomes compared with initiation between 12 and 20 weeks among women with multiple moderate-risk factors for preeclampsia.

STUDY

DESIGN

This retrospective cohort study included singleton pregnancies delivered at ≥20 weeks between 2015 and 2025 at a single academic center. Eligible women had at least two moderate-risk factors for preeclampsia and received daily LDA during pregnancy. Women with high-risk conditions for preeclampsia were excluded. Women were categorized according to aspirin initiation timing: early initiation before 12 weeks (n=1802) and late initiation between 12 and 20 weeks (n=473). Multivariable logistic regression analyses adjusted for maternal age, body mass index, parity, and method of conception.

RESULTS

Early aspirin initiation was associated with significantly lower risks of gestational hypertension (110/1802 [6.1%] vs 118/473 [24.9%]; adjusted odds ratio [aOR] 0.24, 95% confidence interval [CI] 0.18-0.33), preeclampsia (75/1802 [4.2%] vs 74/473 [15.6%]; aOR 0.29, 95% CI 0.20-0.42), and gestational diabetes (273/1802 [15.1%] vs 136/473 [28.8%]; aOR 0.49, 95% CI 0.38-0.63). Early initiation was also associated with lower risks of preterm birth before 32 weeks (5/1802 [0.3%] vs 33/473 [7.0%]; aOR 0.04, 95% CI 0.01-0.10). Neonatal outcomes were improved, including lower risks of low Apgar score at 5 minutes (15/1802 [0.8%] vs 19/473 [4.0%]; aOR 0.26, 95% CI 0.13-0.56) and neonatal intensive care unit admission (338/1797 [18.8%] vs 147/462 [31.8%]; aOR 0.52, 95% CI 0.41-0.67).

CONCLUSION

Initiation of LDA before 12 weeks of gestation was associated with reduced risks of hypertensive disorders of pregnancy, preterm birth, and neonatal morbidity compared with initiation between 12 and 20 weeks.