Multiple Chronic Conditions Before Pregnancy and Risk of Adverse Maternal Health Outcomes: Population‐Based Cohort Study

Objective To assess the risks of perinatal emergency department (ED) use, hospitalisation and severe maternal morbidity or mortality (SMM‐M) associated with preconception MCC, according to the number of chronic conditions, complex MCC and co‐occurring cardiometabolic conditions. Design Population‐based cohort study. Setting Ontario, Canada. Population Females aged 13–54 years, with a recognised pregnancy, 2012–2021. Methods Modified Poisson regression was used to generate adjusted relative risks (aRRs) according to the number of chronic conditions, complex MCC (≥ 3 chronic conditions affecting ≥ 3 body systems) and co‐occurring cardiometabolic conditions. aRRs were adjusted for age, parity, income quintile, rurality and immigrant/refugee status. Main Outcome Measures ED use, hospitalisation and SMM‐M from the estimated date of conception to 42 days postpartum. Results In total, 894 042 individuals had no pre‐pregnancy chronic condition; 357 398 had 1; 94 427 had 2; and 27 326 had ≥ 3 chronic conditions. Relative to those without a chronic condition, the aRR for ED use increased with 1 (1.26, 95% CI 1.25–1.27), 2 (1.55, 1.54–1.56) and ≥ 3 (1.86, 1.85–1.88) conditions. For hospitalisations, the corresponding aRRs were 1.45 (1.43–1.47), 2.06 (2.02–2.10) and 3.18 (3.09–3.27). For SMM‐M, the corresponding aRRs were 1.38 (1.35–1.42), 1.82 (1.75–1.90) and 2.75 (2.59–2.92). SMM‐M risk was even more pronounced with complex MCC (aRR 2.92, 95% CI 2.72–3.14), and ≥ 3 cardiometabolic conditions (aRR 5.45, 95% CI 4.29–6.91). Conclusions MCC, especially complex or cardiometabolic MCC, is associated with elevated risk of maternal morbidity. Multidisciplinary patient‐centred care may mitigate these risks.