The diagnostic accuracy of external pelvimetry and maternal height to predict dystocia in nulliparous women: a study in Cameroon.

OBJECTIVE: In many developing countries, most women deliver at home or in facilities without operative capability. Identification before labour of women at risk of dystocia and timely referral to a district hospital for delivery is one strategy to reduce maternal and perinatal mortality and morbidity. Our objective was to assess the prediction of dystocia by the combination of maternal height with external pelvimetry, and with foot length and symphysis-fundus height. DESIGN: A prospective cohort study. SETTING: Three maternity units in Yaoundé, Cameroon. POPULATION: A total of 807 consecutive nulliparous women at term who completed a trial of labour and delivered a single fetus in vertex presentation. METHODS: Anthropometric measurements were recorded at the antenatal visit by a researcher and concealed from the staff managing labour. After delivery, the accuracy of individual and combined measurements in the prediction of dystocia was analysed. MAIN OUTCOME MEASURES: Dystocia, defined as caesarean section for dystocia; vacuum or forceps delivery after a prolonged labour (>12 hours); or spontaneous delivery after a prolonged labour associated with intrapartum death. RESULTS: Ninety-eight women (12.1%) had dystocia. The combination of a maternal height less than or equal to the 5th percentile or a transverse diagonal of the Michaelis sacral rhomboid area less than or equal to the 10th percentile resulted in a sensitivity of 53.1% (95% CI 42.7-63.2), a specificity of 92.0% (95% CI 89.7-93.9), a positive predictive value of 47.7% (95% CI 38.0-57.5) and a positive likelihood ratio of 6.6 (95% CI 4.8-9.0), with 13.5% of all women presumed to be at risk. Other combinations resulted in inferior prediction. CONCLUSION: The combination of the maternal height with the transverse diagonal of the Michaelis sacral rhomboid area could identify, before labour, more than half of the cases of dystocia in nulliparous women.