Intellectual and developmental disability diagnoses in California delivery records and adverse maternal outcomes

Background: Women with intellectual and developmental disability (IDD) are a population whose maternal health outcomes remain poorly documented. We estimated associations between maternal IDD diagnosis in California birth records and adverse maternal outcomes, and assessed whether prenatal clinical characteristics mediate these relationships. Methods: This retrospective population-based cohort study included all deliveries ≥22 weeks' gestation in California between 2007 and 2021, using birth and fetal death certificates linked to inpatient and emergency department records. Outcomes included severe maternal morbidity (SMM), cesarean delivery, preeclampsia, and maternal hospital admission in the year following delivery. We calculated adjusted risk ratios (aRRs) matched on maternal age and year of delivery. We examined IDD as a single category and by subtype: autism spectrum disorder (ASD), cerebral palsy (CP), intellectual disability (ID), chromosomal differences, and other IDDs. Mediators included tobacco use, pre-existing hypertension, pre-existing diabetes, preeclampsia, prepregnancy body mass index, epilepsy, depression/anxiety, bipolar disorder or schizophrenia, and adequate prenatal care. Results: Among 6,435,742 singleton births, 4492 mothers (0.07%) had an IDD diagnosis. Women with IDD faced elevated risks across all adverse outcomes compared to those without: SMM-aRR: 2.77, 95% CI: 2.40, 3.19; cesarean delivery-aRR: 1.44, 95% CI: 1.39, 1.50; preeclampsia-aRR: 2.52, 95% CI: 2.30, 2.77; and hospital admission within 1 year of delivery-aRR: 4.64, 95% CI: 4.26, 5.05. While risk was elevated for all subtypes across all outcomes, ID tended to confer the highest risk. In the mediation analysis, hypertensive disorders and mental health conditions were the strongest individual mediators. In a joint mediation analysis, select perinatal characteristics explained half of the excess risk of cesarean delivery (autism), preeclampsia (autism), hospital admission (ID), and SMM (ID). Conclusions: Women with IDD documented in California birth records face substantially elevated risks of adverse maternal outcomes, with the largest disparities in hospital admission in the year following delivery. Hypertensive disorders, depression, and anxiety were the strongest potential mediators of those analyzed, and should be further evaluated as intervention targets. Given our reliance on inpatient diagnostic codes, findings may generalize most reliably to women with IDD with the highest support needs.