A retrospective analysis of the risk factors for vacuum-assisted vaginal deliveries and outcomes following mid/low cavity and perineal applications

Introduction: Assisted vaginal birth (AVB) refers to the obstetric procedure commonly performed during the second stage of labor, aimed to expedite delivery after evaluating alternatives options of cesarean birth or expectant management. Objective: To evaluate the risk factors for AVB and to compare perinatal factors and outcomes of vacuum extraction when applied to the mid/low cavity versus the perineum. Study design: Retrospective observational monocentric study conducted on the cohort of women with singleton pregnancies who delivered vaginally in 2023 at the Fondazione IRCCS Ca’ Granda Ospedale Maggiore Policlinico in Milan. Multivariable logistic regression was used to identify factors independently associated with AVB. A secondary analysis compared maternal and neonatal outcomes between perineal and mid/low cavity vacuum applications. Results: A total of 3455 vaginal births were included: 3090 spontaneous vaginal births and 365 AVB. After adjusting for all factors considered, maternal age (OR 1.04, 95% CI: 1.01–1.07), mode of conception (OR 1.58, 95% CI: 1.07–2.33), epidural analgesia (OR 6.25, 95% CI: 3.05–12.80), gestational age (OR 1.48, 95% CI: 1.31–1.67), and newborn male sex (OR 1.35, 95% CI: 1.06–1.73) were positively associated with AVB, whereas parity (OR 0.20, 95% CI: 0.14–0.29) was inversely associated. Compared to perineal applications, mid/low pelvic applications were associated with greater blood loss (p < 0.01), higher episiotomy rate (95.5% vs 88.2%, p = 0.03), and increased ultrasound use (62.4% vs 23.5%, p < 0.01). Conclusions: In this real-world cohort, AVB was mainly associated with well-established factors, confirming previous evidence. Mid/low cavity applications showed greater maternal morbidity than perineal applications, underscoring the importance of careful case selection and procedural planning.