Reported Outcomes for Assisted Vaginal Birth: A Systematic Review.

OBJECTIVE: To systematically catalog all procedural, maternal, and neonatal outcomes reported in contemporary assisted vaginal birth literature, quantify their reporting frequency, and describe definitions used, to form the basis for development of a core outcome set for assisted vaginal birth. DATA SOURCES: A comprehensive search of MEDLINE, EMBASE, and the Cochrane Library was conducted to identify studies published between January 2001 and September 2025. METHODS OF STUDY SELECTION: Studies reporting outcomes related to use of forceps, vacuum, and spatula were eligible. Studies that included 30 participants or more in any health care setting and were published in any language were included. Two reviewers independently conducted study selection, data extraction, and quality assessment, with narrative synthesis undertaken. TABULATION, INTEGRATION, AND RESULTS: Overall, 206 studies were included. Outcomes were grouped into procedural (n=2 outcomes), maternal (n=40 outcomes), and neonatal (n=53 outcomes) domains. Definitions for outcomes varied widely and were inconsistently described. The majority of outcomes were reported in fewer than 20 studies. Outcomes reported most frequently were obstetric anal sphincter injury (n=147 studies), episiotomy (n=99 studies), neonatal intensive care unit (NICU) or special care nursery admission (n=90), low Apgar score (n=90 studies), unsuccessful assisted vaginal birth (n=74 studies), and postpartum hemorrhage (n=74 studies). Crude unadjusted prevalence data included unsuccessful assisted vaginal birth rates of 9.4% for forceps and 6.7% for vacuum extractor. Postpartum hemorrhage was more common after forceps birth (9.0%) than vacuum extractor birth (3.9%), as was obstetric anal sphincter injury (18.2% vs 10.8%). Episiotomy was frequently performed with both instruments (69.4% forceps, 62.0% vacuum extractor). Forceps births had a higher prevalence of NICU or special care baby unit admission (10.0% vs 7.1%). Overall, serious neonatal complications were uncommon for both instruments. Long-term maternal and neonatal outcomes were infrequently reported. CONCLUSION: Outcome reporting in assisted vaginal birth research is highly heterogeneous, with substantial variation in outcome definitions. This lack of standardization limits evidence synthesis and complicates clinical interpretation. These findings provide a foundation for developing a core outcome set for assisted vaginal birth to improve reporting consistency and to support future research and clinical decision making. SYSTEMATIC REVIEW REGISTRATION: PROSPERO, CRD420251170593.