Effect of vaginal delivery on anal sphincter function in Asian primigravida: a prospective study

Introduction and hypothesis The true incidence of obstetric anal sphincter injuries (OASI) among Asian primigravida is not known. This study aimed to evaluate OASI in Sri Lankan primigravida. Methods One hundred and one consecutive primigravida in their last trimester were recruited from antenatal clinics at a tertiary care centre in Sri Lanka and followed up 6 weeks and 6 months after delivery. They were assessed using anorectal manometry (3D-ARM) and endoanal ultrasound (3D-EAUS) on both occasions. Results Seventy-three (75.3 %) had vaginal delivery without instrumentation, whereas 3 (3.1 %) each delivered using forceps or vacuum. Twelve (12.4 %) had emergency caesarean sections and 6 (6.2 %) had elective caesarean sections. None had clinically identified anal sphincter injuries. EAUS identified IAS defects in 3 (5.1 %) and EAS defects in 28 (47.5 %). Both resting ( p = 0.3) and squeeze ( p = 0.001) pressures had decreased following childbirth. Multivariate analysis identified antepartum RP and postpartum EAS defects to be associated with RP reduction (χ 2 (4)=17.825, p