Low-Dose Aspirin for Preventing Birth of a Small-For-Gestational Age Neonate in a Subsequent Pregnancy

OBJECTIVE: To estimate whether low-dose aspirin use is associated with an altered risk of delivering a small-for-gestational age (SGA) neonate among women with a history of having an SGA neonate in a prior pregnancy. METHODS: We performed a Swedish register-based cohort study including women in their second pregnancy who had a history of having an SGA neonate (birth weight less than the 10(th) percentile). The association between use of low-dose aspirin in subsequent pregnancy and birth of an SGA neonate or a severely SGA neonate (birth weight less than the third percentile) were estimated using inverse propensity-weighted estimation, accounting for potential confounders. RESULTS: Among 8,416 women who gave birth to an SGA neonate in their first pregnancy, 801 (9.5%) used low-dose aspirin during their second pregnancy. The incidence of SGA neonates was similar among women using low-dose aspirin (21.7%) and those who did not use aspirin (20.7%). Low-dose aspirin use in pregnancy was not associated with an altered risk of having an SGA neonate (adjusted relative risk [aRR] 0.86, 95% CI 0.67-1.10) or a severely SGA neonate (aRR 0.98, 95% CI 0.71-1.34). Given the strong association between preeclampsia and SGA, we performed subgroup analyses based on preeclampsia status. Among women who had an SGA neonate and co-existing preeclampsia in their first pregnancy, low-dose aspirin was not associated with an altered risk of having an SGA (aRR 0.83, 95% CI 0.63-1.10) or severely SGA (aRR 1.02, 95% CI 0.73-1.44) neonate. Additionally, no association was seen among women who developed preeclampsia in their second pregnancy. CONCLUSION: Among women with a history of having an SGA neonate, low-dose aspirin was not associated with a decreased risk of having an SGA or severely SGA neonate in subsequent pregnancy. These findings suggest that low-dose aspirin should not be used to prevent recurrent SGA.