Position at birth as an important factor for the occurrence of anal sphincter tears: a retrospective cohort study

Objective: This work aimed to analyze the association between maternal position at birth in spontaneous deliveries and the occurrence of anal sphincter tears (AST) given the lack of evidence related to the least traumatic birth position. Study design: A total of 7832 vaginal deliveries were included. Vaginal-operative deliveries and deliveries with fundal pressure were excluded. Birth positions on bed, in water, kneeling, and in a squatting position on a low stool were compared. Birth position on bed was considered as the reference group, and a logistic regression analysis adjusting for important fetomaternal parameters was performed. Results: The overall incidence of AST was 1.1%. AST rate was significantly increased in squatting (2.9%) and kneeling (2.1%) positions compared with birth position on bed (1.0%) or in water (0.9%). Logistic regression analysis revealed a significantly higher risk for ASTs in squatting (OR 2.92, CI 95% 1.04-8.18) and in kneeling positions (OR 2.14, CI 95% 1.05-4.37) compared with the reference group on bed. When adjusting for risk factors, birth in a kneeling position remained significantly associated with ASTs (adj. OR 2.21, CI 95% 1.07-4.54). Conclusions: Birth in squatting or in kneeling position is associated with an elevated risk for ASTs. Birth in water is not associated with an increased risk for AST. Based on the results, women should be informed about the association of certain birth positions with the occurrence of AST.