Factors Associated with Obstetric Anal Sphincter Injury During Vacuum-Assisted Vaginal Delivery

Henry H Chill; Aharon Dick; Wajdy Zarka; Naama Vilk Ayalon; Joshua I Rosenbloom; David Shveiky; Gilad Karavani

doi:10.1007/s00192-024-05785-5

Factors Associated with Obstetric Anal Sphincter Injury During Vacuum-Assisted Vaginal Delivery

Int Urogynecol J. 2024 May 4. doi: 10.1007/s00192-024-05785-5. Online ahead of print.

Authors

Henry H Chill^#^{1

2}, Aharon Dick^#³, Wajdy Zarka⁴, Naama Vilk Ayalon³, Joshua I Rosenbloom³, David Shveiky^{5

3}, Gilad Karavani³

Affiliations

¹ Female Pelvic Medicine and Reconstructive Surgery (FPMRS), Division of Urogynecology, University of Chicago, Northshore University Health System, 9650 Gross Point Road, Suite 3900, Skokie, IL, USA. henchill@gmail.com.
² Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel. henchill@gmail.com.
³ Department of Obstetrics and Gynecology, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.
⁴ Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.
⁵ Division of Female Pelvic Medicine and Reconstructive Surgery, Department of Obstetrics and Gynecology, Hadassah Medical Center, Faculty of Medicine, Hebrew University of Jerusalem, Jerusalem, Israel.

^# Contributed equally.

PMID: 38703223
DOI: 10.1007/s00192-024-05785-5

Abstract

Introduction and hypothesis: Obstetric anal sphincter injury (OASI) is a major complication associated with vacuum-assisted vaginal delivery (VAVD). The aim of this study was to evaluate risk factors related to vacuum extraction that are associated with OASI.

Methods: This was a case-control study performed at a tertiary university teaching hospital. Included were patients aged 18-45 years who had a singleton pregnancy resulting in a live, term, VAVD. The study group consisted of women diagnosed with OASI following vacuum extraction. The control group included women following VAVD without OASI. Matching at a ratio of 1:2 was performed. Groups were compared regarding demographic, obstetric. and labor-related parameters, specifically focusing on variables related to the vacuum procedure itself.

Results: One hundred and ten patients within the study group and 212 within the control group were included in the final analysis. Patients in the OASI group were more likely to undergo induction of labor, use of oxytocin during labor, increased second stage of labor, higher likelihood of the operator being a resident, increased number of pulls, procedure lasting under 10 min, occipito-posterior head position at vacuum initiation, episiotomy, increased neonatal head circumference, and birthweight. Multivariate logistic regression analysis revealed that increased week of gestation (OR 1.67, 95% CI 1.25-2.22, p < 0.001), unsupervised resident performing the procedure (OR 4.63, 95% CI 2.17-9.90), p < 0.001), indication of VAVD being fetal distress (OR 2.72, 95% CI 1.04-7.10, p = 0.041), and length of procedure under 10 min (OR 4.75, 95% CI 1.53-14.68, p = 0.007) were associated with OASI. Increased maternal age was associated with lower risk of OASI (OR 0.9, 95% CI 0.84-0.98, p = 0.012).

Conclusions: When performing VAVD, increased week of gestation, unsupervised resident performing the procedure, fetal distress as vacuum indication, and vacuum procedure under 10 min were associated with OASI. In contrast, increased maternal age was shown to be a protective factor.

Keywords: Obstetric anal sphincter injury; Operative vaginal delivery; Perineal lacerations; Vacuum delivery; Vacuum-assisted vaginal delivery.