Maternal height and external pelvimetry to predict cephalopelvic disproportion in nulliparous African women: a cohort study

Objective To assess external pelvimetry and maternal height, as predictors of cephalopelvic disproportion. Design Prospective cohort study. Setting Four hospitals in Zaire. Population Six hundred and five nulliparous women. Methods Maternal height and external pelvimetry were assessed during the th ird trimester antenatal visit. Cut off values for considering women at risk for cephalopelvic disproportion were height < 150 cm and external pelvic d istances < 10th centile for the population. Logistic regression analysis, c ombining height and pelvic measurements, was performed to predict women at risk for cephalopelvic disproportion. Main outcome measure Cephalopelvic disproportion was considered when there was caesarean section for failure to progress, vacuum or forceps delivery o r intrapartum stillbirth. Results Cephalopelvic disproportion was present in 42 women. In univariate analysis, height, intertrochanteric diameter and the transverse diagonal of Michaelis sacral rhomboid area were found to be associated with cephalopel vic disproportion. Logistic regression analysis showed that maternal height < 150 cm and/or transverse diagonal < 9.5 cm were the variables most assoc iated with cephalopelvic disproportion. The adjusted odds ratios were 2.2 ( 95% CI0.9 to 5.4) and 6.5 (95% CI 3.2 to 13.2), respectively. The positive predictive value and likelihood ratio were 24% and 4.0 (95% CI 2.8 to 5.8), respectively. The addition of transverse diagonal to maternal height incre ased the sensitivity in predicting cephalopelvic disproportion from 21% to 52%. Conclusion In addition to height, transverse diagonal measurement is able t o predict one out of two cases of cephalopelvic disproportion in nulliparou s women. After validation in a separate cohort, this simple predictive meth od may be used in peripheral centres for timely referral of pregnant women at risk for cephalopelvic disproportion.