Early warning systems to predict severe complications during preterm and postpartum: A scoping review

Early warning systems (EWSs) are widely used in obstetric care to predict severe maternal complications, including postpartum hemorrhage (PPH) and sepsis. However, variations in the definitions of both EWS and target conditions hinder direct comparisons and meta-analyses. This scoping review aimed to systematically identify diagnostic accuracy studies evaluating EWS for predicting severe maternal conditions and to explore trends in this field.

This study followed the Preferred Reporting Items for Systematic reviews and Meta-Analyses extension for Scoping Reviews guidelines. A systematic search of the MEDLINE/PubMed and CENTRAL databases was conducted up to July 12, 2024. Eligible studies included diagnostic accuracy studies assessing EWS in obstetric populations. Two reviewers independently screened studies, extracted data, and summarized study characteristics, including index tests and target conditions.

A total of 93 studies involving 697,558 patients were included. The most frequently evaluated index test was the shock index (SI; 38 studies, 41%), followed by the Modified Early Obstetric Warning Score (19 studies, 20.4%) and the Obstetric Early Warning Score (10 studies, 10.8%). PPH was the most common target condition (46 studies, 49.4%), followed by sepsis (30 studies, 32.3%) and maternal death (21 studies, 22.6%). The combination of SI and PPH was most frequently assessed (20 studies).

Despite the widespread adoption of EWS in obstetric care, the marked heterogeneity in both index tests and outcome definitions highlights the need for standardized criteria and further diagnostic research.