Introduction and hypothesis: Obstetric fistulas are injuries to the genital tract in women without emergency obstetric services. Parity may predict the characteristics of fistulas that affect closure success and residual incontinence. Circumferential fistulas may predispose patients to postoperative incontinence. We hypothesized that primiparous women have more distal fistulas than multiparous women, leading to more scarring and circumferential fistulas.

Methods: A retrospective observational study was conducted on 1,856 women with obstetric fistula evaluated at three sites by three providers. Fistulas were classified using the Goh classification system. Women aged 10 to 55 years were classified as primiparas or multiparas. Analysis by parity of fistula type and size, degree of scarring, and presence of circumferential defect used the Chi squared or Fisher’s exact test, and binary logistic regression.

Results: Of the 1,841 (99.2 %) women included, 878 (47.7 %) were primiparas and 963 (52.3 %) were multiparas. Primiparas were more likely to have distal fistulas, type 4 being most common (31.5 %), whereas multiparas were more likely to have proximal fistulas, most commonly type 1 (48.1 %). Primiparas were more likely to have moderate to severe scarring (11.7 % vs 5.6 %; p < 0.001), and category III (57.1 % vs 39.2 %; p < 0.001), but not to develop circumferential fistulas (5.6 % vs 4.0 %; p = 0.127), be present for repeat surgery (7.1 % vs 7.6 %; p = 0.721), or have ureteric involvement (1.5 % vs 2.2 %; p = 0.301). Multivariate analyses confirmed increased risk with primiparity for distal fistula and scarring.

Conclusions: As hypothesized, primiparas were more likely to have distal fistulas and more scarring, but were not more likely to have circumferential fistulas. Surgeons should plan accordingly.