Severe maternal morbidity and re-hospitalisation in the first postpartum year within Canada, 2008–2020: a population-based retrospective cohort study

Introduction: Severe maternal morbidity (SMM) refers to life-threatening pregnancy-related complications that may have lasting effects on the mother beyond childbirth. Little is known about the impact of SMM on re-hospitalisations in the first year following birth hospitalisation discharge. In this study, we quantified the 1-year risk of maternal re-hospitalisation following birth discharge, comparing SMM-affected to SMM-unaffected individuals. Methods: We conducted a population-based cohort study using hospitalisation data for all live births and stillbirths in Canada, excluding Québec, between 2008 and 2020 to individuals aged 16-55 years. SMM was assessed using a validated measure based on diagnostic and procedure codes for a composite of life-threatening diagnoses during pregnancy beginning at 20 weeks' gestation, during childbirth, or within 42 days following birth hospitalisation discharge. Outcomes were all-cause re-hospitalisation within 42 days of birth hospitalisation discharge and from 43 to 365 days following birth hospitalisation discharge. Log-binomial regression with generalised estimating equations generated unadjusted and adjusted risk ratios (aRRs). We then described causes of re-hospitalisation according to International Classification of Diseases, 10th Revision, Canadian Enhancement chapters, based on the first diagnostic field. Results: There were 3 405 716 births in the study, (mean maternal age 30.0 + 5.5 years and 40% nulliparous), among which 60 260 (1.83%) experienced SMM. Individuals with versus without SMM were more likely to be re-hospitalised within 42 days, with respective rates of 14.6 vs 4.4 per 1000 births (aRR 2.90, 95% CI 2.68 to 3.13). For re-hospitalisation at 43-365 days, respective rates were 62.4 and 29.8 per 1000 births (aRR 1.90, 95% CI 1.84 to 1.96). The most frequent cause of re-hospitalisation in both groups was gallstone disease. Conclusions: Individuals who experience SMM are more likely to be re-hospitalised in the first year following birth hospitalisation discharge, highlighting the need for tailored postpartum care to prevent re-hospitalisation.