Preterm birth and small for gestational age potentiate the association between maternal hypertensive pregnancy and childhood autism spectrum disorder

Children of mothers with hypertensive disorders of pregnancy (HDP) have high rates of preterm-birth (gestational age < 37 weeks) and small-for-gestational-age (SGA), both of which are risk factors of autism spectrum disorder (ASD). This study tested the multiple-hit hypothesis that preterm-birth and SGA in the neonatal period might potentiate the antenatal impact of HDP to increase childhood ASD hazards, and HDP might not be a major contributor. The propensity-score-matched cohort enrolled 18,131 mother–child pairs with HDP and 90,655 normotensive controls between 2004 and 2011. Children with siblings born to the same mothers were excluded for analysis to reduce the potential familial-genetic influence. HDP were classified into chronic-hypertension, gestational-hypertension, preeclampsia, and preeclampsia-with-chronic-hypertension. Using the normotensive group as the reference, the associations between HDP subgroups and the cumulative ASD risks were assessed with hazard ratios, and the effects of preterm-birth and SGA on the associations were examined. The HDP group had a higher cumulative rate of ASD (1.5%) than the normotensive group (1.2%). Preterm-birth and SGA exerted moderating effects to aggravate ASD hazards in children exposed to chronic-hypertension or gestational-hypertension. None of HDP types significantly contributed to ASD after adjustments. In conclusion, antenatal HDP exposure might predispose to ASD outcome through susceptibility to the impact of preterm-birth and SGA.