Migraine, comorbidity, and risks of severe maternal and neonatal morbidity or mortality: A population-based cohort study.

Migraine is a neurological disease associated with adverse perinatal outcomes. We examined the separate and combined impacts of migraine and comorbidity on risks of severe maternal morbidity/mortality (SMM-M) and severe neonatal morbidity/mortality (SNM-M). This population-based cohort study of pregnancies (n=2,643,335) in Ontario, Canada, 2007-2022, compared females with (1) pre-pregnancy migraine and ≥1 other chronic conditions, (2) migraine alone, (3) other chronic conditions alone, and (4) neither migraine/other chronic conditions (referent) using modified Poisson regression. Attributable proportion due to interaction (aAP) reflected additive interaction between migraine and comorbidity. In the cohort, 6.8% had migraine and other chronic conditions, 3.2% migraine alone, 45.7% other chronic conditions alone, and 44.3% neither. The incidence of SMM-M was 1.6%, while SNM-M affected 7.1% of neonates. Risks of SMM-M and SNM-M were greatest in those doubly exposed (aRRSMM-M 1.60, 95% CI 1.54-1.66; aRRSNM-M 1.43, 1.39-1.46), followed by other chronic conditions alone (aRRSMM-M 1.34, 1.32-1.37; aRRSNM-M 1.30, 1.28-1.32), and migraine alone (aRRSMM-M 1.13, 1.07-1.20; aRRSNM-M 1.07, 1.04-1.11). Additive interaction was small for SMM-M (aAP 7.4%, 2.2-12.5) and SNM-M (aAP 3.7%, 0.3-6.9). Although synergistic effects were small, findings suggest individuals with migraine and comorbidity could benefit from preconception and perinatal supports to reduce their risks of perinatal complications.