The effect of antenatal vaginal dilators on perineal trauma: A systematic review and meta-analysis.

Abstract

Background: Vaginal dilators use inflatable balloons that can be gently increased in size to dilate the vagina at a controlled rate before or during delivery.

Objective: The primary objective of this study was to assess if antenatal use of vaginal dilator devices reduces the incidence of the following outcomes: episiotomy, perineal lacerations, anal sphincter injury, and levator ani avulsion.

Search strategy: We identified studies using Embase, Ovid-Medline All, Scopus, Web of Science, and ClinicalTrials.gov from inception to August 28, 2024. We searched for concepts of vaginal dilators or birth training devices, episiotomy, and injuries to the vagina, perineum, pelvic floor musculature, or obstetric anal sphincter.

Selection criteria: We included randomized and non-randomized studies that reported outcomes of interest in participants who used any vaginal dilator device during pregnancy/delivery compared to those who did not. Inclusion criteria were: (1) original clinical research, (2) use of any vaginal dilator device during pregnancy compared to a non-dilator control group and (3) provision of data on at least one of the four outcomes. Exclusion criteria were: (1) publications in languages other than English and French, (2) not peer-reviewed original research and (3) studies that combined dilator use with a second intervention. For meta-analyses, studies were included in each subgroup if they included relevant data.

Data collection and analysis: Two independent readers screened studies for inclusion/exclusion criteria and independently performed data extraction. Primary outcomes included episiotomies, perineal lacerations, anal sphincter injury, and levator ani avulsion. These outcomes were analyzed separately and combined. The Cochrane Q Test and Higgin's I² were used to assess study heterogeneity. Random effects models were used to obtain pooled risk ratios and 95% confidence intervals. Subanalyses were also performed limited to higher-quality studies (i.e., randomized controlled trials with or without birth attendant and outcome assessor blinding) and for each device separately.

Main results: Of 64 screened studies, six were included in the meta-analyses. Antenatal vaginal dilator device reduced incidence of episiotomy compared to no treatment in all studies combined (n = 1262; pooled risk ratio = 0.82 [95% CI: 0.69, 0.98]), but not higher-quality studies (n = 862; pooled risk ratio = 0.90 [95% CI: 0.73, 1.11]). No associations were observed for perineal lacerations, obstetric anal sphincter injury, and levator ani injury in all studies combined or in higher-quality studies. No association was also observed when all outcomes were combined.

Conclusions: Results from our systematic review and meta-analysis do not support a protective effect of antenatal vaginal dilator device use on perineal trauma, especially when limited to the highest-quality studies. However, as our findings were based on the results of only two randomized controlled trials that included birth attendant blinding, additional rigorous studies including birth attendant and outcome assessor blinding are warranted to address this question conclusively.