Objective: To determine whether planned cesarean section (CS) for a second delivery protects anal continence in women with obstetrical anal sphincter lesions. Design: Randomized trial. Setting: 6 maternity units in the Paris area. Sample : Women at high risk of sphincter lesions (first delivery with 3d degree laceration and/or forceps) but no symptomatic anal incontinence. Methods : Endoanal ultrasound was performed in the third trimester of the second pregnancy. Women with sphincter lesions were randomized to planned CS or vaginal delivery (VD). Main outcome measures : Anal continence at 6 months post-partum. Secondary outcomes were urinary continence, sexual morbidity, maternal and neonatal morbidities and worsening of external sphincter lesions. Results : Anal sphincter lesions were detected by ultrasound in 264/434 women enrolled (60.8%) ; 112 were randomized to planned VD and 110 to planned CS. At 6-8 weeks after delivery, there was no significant difference in anal continence between the 2 groups. At 6 months after delivery, median Vaizey scores of anal continence were 1 [IQR 0-4] in the CS group and 1 [IQR 0-3] in the VD group (p = 0.34). There were no significant differences for urinary continence, sexual functions or for other maternal and neonatal morbidities. Conclusions : In women with asymptomatic obstetrical anal sphincter lesions diagnosed by ultrasound, planning a CS had no significant impact on anal continence 6 months after the second delivery. These results do not support advising systematic CS for this indication.