Anthropometric measurements as predictors of cephalopelvic disproportion: Can the diagnostic accuracy be improved?

Objective: We assessed the efficacy of maternal anthropometric measurements and clinical estimates of fetal weight in isolation and in combination as predictors of cephalopelvic disproportion (CPD).

Design: Prospective cohort study.

Setting: Tertiary care teaching hospital, two affiliated hospitals with facilities for conducting cesarean delivery and seven affiliated primary care facilities with no operation theaters.

Sample: Primigravidae over 37 weeks' gestation attending these facilities during a 20-month period with a singleton pregnancy in vertex presentation.

Methods: Several anthropometric measurements were taken in 249 primigravidae. Fetal weight was estimated. Differences in these measurements between the vaginal delivery and CPD groups were analyzed. The validity of these measurements in predicting CPD was analyzed by plotting receiver operating characteristic curves and by logistic regression analysis.

Main outcome measure: Mode of delivery.

Results: Maternal height, foot size, inter-trochanteric diameter and bis-acromial diameter showed the highest positive predictive values for CPD. Combining some maternal measurements with estimates of fetal weight increased predictive values modestly, which are likely to be greater if the estimates of fetal weight are close to the actual birth weight. Based on multivariate analysis the risk factors for CPD in our population were foot length ≤23cm, inter-trochanteric diameter ≤30cm and estimated fetal weight ≥3 000g.

Conclusions: Maternal anthropometric measurements can predict CPD to some extent. Combining maternal measurements with clinical estimates of fetal weight only enhances the predictive value to a relatively modest degree (positive predictive value 24%).