Dzakpasu S, Deb-Rinker P, Arbour L, et al. - Given a lack of international consensus about the definition and components of severe maternal morbidity (SMM), researchers undertook this study to introduce a comprehensive definition of SMM, to build an empirically justified list of SMM types and subtypes, and to apply this to examine SMM in Canada. They utilized data about all hospital deliveries in Canada (excluding Quebec), 2006-2015, to assess candidate SMM types/subtypes. Overall 22,799 cases of SMM subtypes (among 1,418,545 deliveries) that were related to a prolonged length of hospital stay or high case fatality were documented. The composite SMM rate was estimated to be 16.1 per 1000 deliveries between 2012 and 2016. The most common SMM types were identified to be severe pre-eclampsia and HELLP syndrome, and severe postpartum haemorrhage, while the highest case fatality rates among SMM subtypes were reported in women who had cardiac arrest and resuscitation, hepatic failure, dialysis, and cerebrovascular accident/stroke. The application of the proposed definition of SMM and the related list of SMM subtypes for standardised SMM surveillance could be done, with rate ratios and population attributable fractions related to particular SMM types/subtypes serving to notify the clinical practice as well as public health policy.