Risk factors for severe perineal lacerations during childbirth: A systematic review and meta-analysis of cohort studies

Abstract

Aims and objectives: To evaluate and quantify the best available evidence regarding risk factors for severe perineal lacerations.

Background: Many studies have evaluated the risk factors for severe perineal lacerations. However, the results of those studies are inconsistent, and meta-analysis which thoroughly evaluates the risk factors for severe perineal lacerations is still lacking.

Design: Systematic review and meta-analysis of cohort studies based on the PRISMA guideline.

Methods: PubMed, Embase, the Cochrane Library, CINAHL, ClinicalTrials.gov, CNKI, Wanfang Data, VIP and SinoMed were systematically searched for cohort studies reporting at least one risk factor for severe perineal lacerations from 1 January 2000 to 2 June 2021. Two reviewers independently conducted quality appraisal by NOS scale and extracted data. Data synthesis was conducted via RevMan 5.3 using a random-effects or fixed-effects model.

Results: A total of 47 studies with 7,043,218 women were included. The results showed that prior caesarean delivery (OR: 1.46, 95% CI 1.12-1.92) and pre-pregnant underweight (OR: 1.31, 95% CI 1.22-1.41) significantly increased the risk of severe perineal lacerations. The results also demonstrated that episiotomy was protective against severe perineal lacerations in forceps delivery (OR: 0.56, 95% CI 0.42-0.74), but not spontaneous vaginal delivery (OR: 1.30, 95% CI 0.81-2.07) or vacuum delivery (OR: 0.76, 95% CI 0.45-1.28). Nulliparity, foetus in occipitoposterior or occipitotransverse position, and midline episiotomy were also independent risk factors for severe perineal lacerations.

Conclusions: Severe perineal lacerations are associated with many factors, and evidence-based risk assessment tools are needed to guide the midwives and obstetricians to estimate women's risk of severe perineal lacerations.

Relevance to clinical practice: This systematic review and meta-analysis identified some important risk factors for severe perineal lacerations, which provides comprehensive insights to guide the midwives to assess women's risk for severe perineal lacerations and take appropriate preventive measures to decrease the risk.

Keywords: OASIs; VBAC; risk; severe perineal lacerations; vaginal birth after caesarean delivery.