Variation in outcome reporting in studies comparing vacuum-assisted birth versus second-stage caesarean section: a systematic review

To assess the variations and quality of maternal and neonatal outcomes reported in studies on vacuum devices vs second-stage caesarean section through a systematic review. We searched major databases were searched from inception to January 2025. Two reviewers independently screened studies and extracted data. We grouped maternal and perinatal outcomes were grouped into mortality or morbidity and process or care-related categories, with 33 predefined categories and 62 subcategories. Frequencies were summarised as proportions, and outcome reporting quality was assessed using a modified Harman’s questionnaire. We determined the associations between study characteristics and reporting quality through multilevel mixed-effects models. The protocol was registered (PROSPERO CRD42024469164). Twenty-three studies including over 2.6 million women reported 352 outcomes (132 primary; 220 secondary). The frequently reported maternal outcomes were urogenital tract injury (40/137, 29.2%) and postpartum haemorrhage (32/137, 23.4%), while Apgar score (24/215, 7%) and musculoskeletal injury (22/215, 6%) were the most common neonatal outcomes. Most outcomes scored 2/3 on the modified Harman’s questionnaire, with no significant improvement in reporting quality over time. Maternal outcomes had significantly higher quality scores than neonatal outcomes (β = 0.18, p = 0.002, 95% CI 0.06 to 0.29). Study setting was significantly associated with total quality scores, with studies from middle-income countries showing lower scores compared with those from high-income countries (β = –1.73, p = 0.003, 95% CI –2.88 to –0.57). There was no association between reporting quality and study size, outcome type (primary or secondary), or journal impact factor. Outcomes reporting quality varied considerably. Standardisation through a core outcome set is needed to improve comparability, evidence synthesis, and research quality on outcomes of vacuum-assisted births. • This is the first study to quantify the variations in the reporting of immediate clinical maternal and perinatal outcomes and their quality in studies comparing effectiveness and safety of vacuum devices vs second-stage caesarean sections. • Outcome reporting in this field is currently heterogeneous and should be standardised. • Quality of outcome reporting differed between maternal and neonatal outcomes and by setting but not by outcomes type (primary and secondary) or journal impact factor.