Commentary on ‘Pelvimetry and prevention of obstetric fistula: start with the basics’
Browning and colleagues have revisited the prospect of using an easily measured pelvic dimension, the intertuberous measurement, to predict which women will have obstructed labour and develop obstetric fistula. This small, retrospective study demonstrates that both the fistula index (number of knuckles × height) and the number of knuckles alone were significantly lower in fistula patients when compared with those who delivered normally. One need only pass through a typical obstetric fistula ward and see our patients to surmise these findings. However, these findings have been well validated by this study with highly significant differences between groups, especially for the intertuberous diameter. This study benefits from a simple design and practical measurements, which any healthcare provider can perform. The study is limited by small size and by the fact that the examiner was not blinded to the groups. Also, cases and controls were not matched, though there was no overall statistically significant difference in gravity, parity and age between groups.
The design illustrates well only the first step in studying a relatively uncommon condition—estimated prevalence of obstetric fistula 188 per 100 000 women in low-resource settings (Stanton et al. Int J Gynaecol Obstet 2007;99:S4–S9) by looking backwards towards some plausible exposures that may have contributed to the outcome. These retrospective findings encourage us to look forward in time with a large group of women in whom simple pelvic measurements are taken and then determine which patients go on to obstructed labour. As noted by the authors, it would be both impractical and probably unethical to use obstetric fistula as an outcome in a prospective analysis, so obstructed labour would be the best proxy. Quality prospective research is largely neglected in obstetric fistula patients because they are a vulnerable and disenfranchised group. If obstetric fistula were a disease of the wealthy, we would have thousands of studies dedicated to its eradication. Instead, we have a handful of prospective studies, some well-performed cohorts and a host of observational accounts.
In the end, it will still be difficult to draw any causal association between small pelvis, as measured by the intertuberous diameter, and development of obstetric fistula. The challenge will be to determine which variables are sufficiently predictive of obstructed labour to warrant the time and cost of finding these women before labour and referring them to a maternity waiting home with an adjacent health facility that performs cesarean deliveries so as to avoid unchecked labour in these patients at all cost. However, this remains the pervasive challenge for all high-risk conditions in low-resource settings that lead to maternal and neonatal morbidity and mortality. Women with undiagnosed pre-eclampsia, previous cesarean delivery, malpresentation or multiple gestation, undiagnosed or poorly controlled HIV and many other conditions also remain at high risk of death or disability. In fact, most poor obstetric outcomes still occur to those women in whom no specific risk factor exists. Helpful predictors of obstructed labour and other obstetric tragedies may be useful stop-gap measures towards the ultimate goal of having safe, local obstetric care for all women independent of where they live or how much they earn.