Predicting women at risk for developing obstetric fistula: a fistula index? An observational study comparison of two cohorts




To ascertain if a predictor of obstructed labour and obstetric fistula (OF) occurrence could be devised.


Observational study of two cohorts.


Selian Lutheran Mission Hospital, Arusha, Tanzania and Aberdeen Women's Centre, Freetown, Sierra Leone.


All women presenting with OF caused by obstructed labour and all women having a normal vaginal delivery (NVD) at both institutions were eligible for the study.


All women with OF and those delivering normally had their height in centimetres measured and their intertuberous space measured by the number of examiner's knuckles admitted. The dimensions for OF and normal delivery were examined individually and multiplied to gain a ‘fistula index’.

Main outcomes measures

Dimensions and index were compared statistically between OF and NVD women using t tests. Sensitivity, specificity and predictive values from receiver operating characteristic curves were obtained for predicting OF.


There were statistical differences between the groups with OF women being significantly shorter, having a smaller intertuberous space and lower fistula index than those undergoing NVD (each < 0.001). Sensitivity was high for fistula index ≤ 507.5 (94.9%, 95% confidence interval 83.1–98.6%) and for intertuberous space of at least three knuckles (92.3%, 95% CI 79.7–97.3%) alone.


A simple antenatal measurement of intertuberous space could screen those women at higher risk of needing medical intervention to prevent OF.