Summary
Dr. Chapa reviews the ASPIRIN trial published in The Lancet (January 2020) examining whether low-dose aspirin can reduce preterm birth in nulliparous women. This multi-country, double-blind, placebo-controlled trial of nearly 12,000 women from six low-to-middle income countries found that 81 mg aspirin started very early in pregnancy (6-13 weeks) reduced preterm birth from 13.1% to 11.6%, a statistically significant result. Beyond the primary outcome, aspirin also significantly reduced perinatal mortality, fetal loss after 16 weeks, and early preterm birth before 34 weeks. The episode contextualizes these findings with earlier 2017-2018 data showing 7-35% reductions in preterm birth across multiple studies. Chapa notes the growing push for universal aspirin use in pregnancy given its low cost, favorable safety profile, and expanding evidence base beyond just preeclampsia prevention.
Key Points
- The ASPIRIN trial (Lancet, 2020) of ~12,000 nulliparous women showed 81 mg aspirin reduced preterm birth from 13.1% to 11.6% (relative risk 0.89)
- Aspirin was started very early (6-13 weeks gestation), earlier than ACOG's standard 12-16 week recommendation for preeclampsia
- Additional benefits included significant reductions in perinatal mortality, fetal loss after 16 weeks, and early preterm birth (<34 weeks)
- Aspirin works through antiplatelet action, improving placental blood flow by reducing thromboxane and increasing prostacyclin
- Earlier studies showed 7-35% reductions in preterm birth; a 2017 trial found 35% reduction in recurrent preterm labor
- Daily low-dose aspirin in pregnancy shows no adverse fetal effects at doses under 150 mg and does not increase congenital malformations
- There is a growing push for universal aspirin use in all pregnancies regardless of risk factors due to cost-effectiveness data
Key Moments
ASPIRIN Trial Shows Significant Preterm Birth Reduction
The Lancet ASPIRIN trial found that early low-dose aspirin reduced preterm birth from 13.1% to 11.6% with additional reductions in perinatal mortality and early preterm delivery.
"preterm birth before 37 weeks occurred in 11.6% of women who took aspirin compared to 13.1% who took placebo. That p-value was 0.012, meaning it was significant, and the relative risk was 0.89"
How Aspirin Improves Placental Blood Flow
Explanation of aspirin's mechanism in pregnancy, reducing thromboxane and increasing prostacyclin to improve placental vascular formation, with growing evidence it reduces preterm birth even in low-risk women.
"Aspirin is an antiplatelet agent that improves blood flow and vascular formation in the placenta by reducing the thromboxane and increasing the vasodilator prostacyclin"
The Push for Universal Aspirin in Pregnancy
Dr. Chapa discusses the growing movement toward universal aspirin use in all pregnancies regardless of risk factors, citing cost-effectiveness data and the accumulating evidence for benefits beyond preeclampsia.
"there's such a push now from thought leaders, researchers, and the published literature for universal aspirin use in pregnancy"
