Preventability of Severe Maternal Morbidity: A Scoping Review of the Literature in High-Income Countries

Severe maternal morbidity (SMM) affects 0.5 to 4% of pregnancies in the United States and other high-income countries (HIC). Research examining SMM preventability is limited but has emerged following recommendations from professional organizations to identify and review SMM events, determine preventability, and derive recommendations for care improvement. This study examined existing evidence on SMM preventability in HICs, synthesizing definitions, assessment approaches, and preventability rates.

A scoping literature review was conducted using the Joanna Briggs Institute methodology and Preferred Reporting Items for Systematic Reviews Extension for Scoping Reviews guidelines. Four databases (PubMed, Embase, Scopus, and Cochrane) were searched from January 2011 to June 2024 using terms related to SMM and preventability. Eligible studies reported SMM preventability estimates in HICs. Two reviewers independently screened articles and extracted data. Content analysis assessed methodological patterns, and narrative synthesis identified conceptual frameworks.

Of the 1,835 studies identified, 53 underwent full-text review, and 19 studies met inclusion criteria, primarily from the United States (52.6%) and New Zealand (26.3%). Studies showed diverse assessment approaches, with 47.4% using Geller-based frameworks, and three distinct classification methods. SMM preventability ranged from 21 to 76% (weighted average: 47.9%) for events deemed preventable, potentially preventable, or where care improvements were identified. Preventability rates varied by primary cause, being highest for sepsis (25-68%, average: 57.1%), followed by hemorrhage (22-72%, average: 45.2%), hypertensive disorders (22-73%, average: 43.6%), and cardiovascular events (13-49%, average: 38.9%). Across four studies, external reviews consistently identified higher SMM preventability rates than internal facility reviews.

This review revealed substantial methodological heterogeneity in SMM preventability assessment across HICs, with up to three-quarters of events having improvement opportunities. Despite variation, most studies identified substantial preventability, demonstrating the feasibility and value of conducting SMM preventability reviews. Standardized definitions and review processes are needed to enhance cross-study comparisons and establish evidence-based improvement targets.

· SMM preventability assessments lack standardization.. · A wide range (21-76%) of SMM events are preventable.. · Higher SMM preventability with external versus internal facility reviews..