Abstract Objective This is a prospective study to review the natural history of anorectal dysfunction after primary repair for third or fourth degree obstetric tear and to identify the predictive factors for significant faecal incontinence. Method From January 2003 to December 2005, 121 consecutive women (mean age 29.9 ± 4.7) who sustained third or fourth degree obstetric tears were assessed. All had primary repair by obstetricians. They were assessed using anorectal physiology testing and endoanal ultrasound. Short-term (3-month postpartum) and medium-term (mean 18.8 ± 7.7 months) Wexner’s continence scores were obtained. Results Among the 121 women, seven were excluded because of incomplete follow-up. At short-term assessment, 25 out of 114 women were incontinent. One of them underwent another sphincter repair for significant faecal incontinence. Twenty-one and three patients respectively, had mild (Wexner’s score 1–4) and moderate (Wexner’s score 5–8) symptoms. At medium-term assessment, 24 patients remained incontinent; of these, 20 had mild symptoms (Wexner’s score 1–4) and four had moderate incontinence (Wexner’s score 5–8). The parity (P =0.04), degree of obstetric tear (P =0.036) and short-term Wexner’s scores at 3 months postpartum (P <0.0001) were significantly related to the change in Wexner’s scores at medium-term assessment. However, the short-term Wexner’s score was the only identifiable predictive factor for significant faecal incontinence. Conclusion Most women suffering from third or fourth degree obstetric tear were continent or mildly incontinent. Poor Wexner’s score at short-term assessment at 3 months postpartum was predictive of faecal incontinence in the medium-term.