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

Background: 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 assisted vaginal births (AVB) and to compare perinatal factors and outcomes of vacuum extraction applied at the mid/low cavity and at the perineum. Study design : Retrospective observational monocentric study conducted on the cohort of women who delivered vaginally in 2023 at the Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico in Milan. Results : A total of 3833 vaginal births were included: 3090 uneventful vaginal births and 365 assisted vaginal births. 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 : Increased maternal age, nulliparity, medically assisted conception, epidural analgesia, gestational age, and newborn male sex were identified as potential risk factors for AVB. Vacuum extractions performed at mid/low pelvic stations were associated with higher use of episiotomy and greater blood loss. These findings may help in risk awareness and a personalized labor management.