Has the prevalence of levator avulsion after forceps delivery changed over the last six decades? : a retrospective study in a urogynaecological population

Objective: Forceps delivery is associated with a higher risk of maternal birth trauma. It is speculated that it is due to sub-optimal use of forceps in inexperienced hands. The aim of this study was to determine the association between time of forceps birth and prevalence of levator avulsion over the last six decades. Study Design: This was a retrospective analysis of datasets of women with a history of forceps delivery, seen at a tertiary urogynaecological centre between January 2014 and August 2018. They had undergone a standardized interview, clinical examination and four-dimensional translabial ultrasound. Archived imaging data was reviewed for levator avulsion offline at a later date, blinded against all clinical data. Associations between levator avulsion, maternal age at first vaginal birth, the weight of the first vaginally born baby, and time since forceps delivery categorised by decade were tested by univariable analysis. Factors found to be significant on univariable analysis were included in a multivariable logistic regression model to test the association between prevalence of levator avulsion and time of forceps delivery while controlling for confounders. Results: In total, 2026 patients were seen during the study period. Among them 511 (25.2%) had a history of forceps delivery. Fourteen volume datasets were incomplete or missing, leaving 497 complete datasets for analysis. Mean age at presentation was 58 ± 12 years (23–91). Mean body mass index was 29 ± 6 kg/m2. Mean age at first delivery was 25 ± 5 years. Mean birth weight of the first vaginal birth was 3454 ± 557 g. 457 women (92%) had had one forceps delivery, 31 had two forceps deliveries (6%) and 9 had three forceps deliveries (2%). Mean time interval between forceps delivery and assessment was 32 ± 13 years (0.3–64.8). 229 women (46%) were diagnosed with levator avulsion. The prevalence of avulsion after forceps increased significantly from 34% to 56% between 1950 and 2017 (P = 0.04). However this difference became insignificant when controlling for maternal age at 1st vaginal delivery and birth weight. Conclusions: We found no evidence of a changed prevalence of levator avulsion at forceps delivery over the last 67 years