Importance: Epidural labor analgesia (ELA) has been associated with an increased offspring risk of autism spectrum disorder (ASD). Whether this finding may be explained by residual confounding remains unclear.
Objective: To assess the association between ELA and offspring risk of ASD.
Design, setting, and participants: Longitudinal cohort study of vaginal deliveries of singleton live infants born from 2005 to 2016 from a population-based data set linking information from health care databases in Manitoba, Canada; offspring were followed from birth until 2019 or censored by death or emigration. Data were analyzed from October 19, 2020, to January 22, 2021.
Exposures: Epidural labor analgesia.
Main outcomes and measures: At least 1 inpatient or outpatient diagnosis of ASD in offspring aged at least 18 months. For the full population and a sibling cohort, inverse probability of treatment-weighted Cox proportional hazards regression analyses were used to control for potential confounders.
Results: Of the 123 175 offspring included in this study (62 647 boys [50.9%]; mean [SD] age of mothers, 28.2 [5.8] years), 47 011 (38.2%) were exposed to ELA; 2.1% (985 of 47 011) of exposed vs 1.7% (1272 of 76 164) of unexposed offspring were diagnosed with ASD in the follow-up period (hazard ratio [HR], 1.25; 95% CI, 1.15-1.36). After adjusting for maternal sociodemographic, prepregnancy, pregnancy, and perinatal covariates, ELA was not associated with an offspring risk of ASD (inverse probability of treatment-weighted HR, 1.08; 95% CI, 0.97-1.20). In the within-siblings design adjusting for baseline covariates, ELA was not associated with ASD (inverse probability of treatment-weighted HR, 0.97; 95% CI, 0.78-1.22). Results from sensitivity analyses restricted to women without missing data who delivered at or after 37 weeks of gestation, firstborn infants only, and offspring with ASD classified with at least 2 diagnostic codes were consistent with findings from the main analyses.
Conclusions and relevance: In a Canadian population-based birth cohort study, no association between ELA exposure and an increased offspring risk of ASD was found.