Severe maternal morbidity and infant mortality in Canada

Background — Severe maternal morbidity (SMM) comprises an array of conditions and procedures denoting an acutely life-threatening pregnancy-related condition. SMM may further compromise fetal well-being. Empirical data are lacking about the relation between SMM and infant mortality.

Methods — This population-based cohort study included 1 892 857 singleton births between 2002 and 2017 in Ontario, Canada, within a universal healthcare system. The exposure was SMM as an overall construct arising from 23 weeks’ gestation up to 42 days after the index delivery. The primary outcome was infant mortality from birth to 365 days. Multivariable modified Poisson regression generated relative risks and 95% confidence intervals (CIs), adjusted for maternal age, income, rurality, world region of origin, diabetes mellitus, and chronic hypertension.

Results — Infant mortality occurred among 174 of 19 587 live births with SMM (8.9 per 1000) vs 5289 of 1 865 791 live births without SMM (2.8 per 1000) (an adjusted relative risk of 2.93 [95% CI 2.51–3.41]). Of 19 587 pregnancies with SMM, 4523 (23.1%) had sepsis. Relative to births without SMM, the adjusted odds ratio for infant death from sepsis was 1.95 (95% CI 1.10–3.45) if SMM occurred without maternal sepsis and 6.36 (95% CI 3.50–11.55) if SMM included sepsis.

Conclusions — SMM confers a higher risk of infant death. There is also coupling tendency (concurrent event of interest) between SMM with sepsis and infant death from sepsis. Identification of preventable SMM indicators, as well as the development of strategies to limit their onset or progression, may reduce infant mortality.