Does aspirin prescribed to women deemed high risk for preterm pre‐eclampsia at 11–13+6 weeks gestation affect the prevalence of small for gestational age neonates?

Background Aspirin has been shown to reduce prevalence of both early‐onset pre‐eclampsia (ePET) and fetal growth restriction (FGR). Aims To determine whether aspirin prescribed for risk of ePET reduces the prevalence of small for gestational age (SGA) neonates. Material and Methods Two prospective cohorts were consecutively recruited in a large university hospital in Sydney. The Observational cohort (April 2010 to March 2012) validated an algorithm for ePET screening, where risk for ePET was modelled on history, mean arterial pressure, uterine artery pulsatility index and pregnancy‐associated plasma protein A. The Interventional cohort (April 2012 to December 2017) were screened and allocated women at high risk of developing ePET to aspirin 150 mg. The prevalence of preterm and term SGA was compared using regression analysis. Result There were 3013 and 8424 women screened in the Observational and Interventional cohorts respectively. Women who screened high risk for ePET were three to four times more likely to give birth to a neonate classified as SGA in the Observational (6.8% vs 1.9%) and Interventional cohorts (6.0% vs 1.8%). In women who screened high risk, there were no statistically significant differences in the prevalence of SGA neonates (6.6% vs 6.0%; adjusted odds ratio 0.84 (0.50–1.42)) in women who received aspirin compared to women who did not. Conclusions Women who screen high risk for ePET have an increased chance of delivering an SGA infant. A reduction in the prevalence of SGA neonates when aspirin was prescribed to women who screened high risk for ePET did not reach clinical significance in our cohort.