Diagnostic accuracy of maternal anthropometric measurements as predictors for dystocia in nulliparous women

BACKGROUND Dystocia is one of the important causes of maternal morbidity and mortality in low-income countries. This study was aimed to determine the diagnostic accuracy of maternal anthropometric measurements as predictors for dystocia in nulliparous women. MATERIALS AND METHODS This prospective cohort study was conducted on 447 nulliparous women who referred to Omolbanin hospital. Several maternal anthropometric measurements such as height, transverse and vertical diameters of Michaelis sacral rhomboid area, foot length, head circumference, vertebral and lower limb length, symphysio-fundal height, and abdominal girth were taken in cervical dilatation ≤ 5 cm. Labor progression was controlled by a researcher blind to these measurements. After delivery, the accuracy of individual and combined measurements in prediction of dystocia was analyzed. Dystocia was defined as cesarean section and vacuum or forceps delivery for abnormal progress of labor (cervical dilatation less than 1 cm/h in the active phase for 2 h, and during the second stage, beyond 2 h or fetal head descend less than 1 cm/h). RESULTS Among the different anthropometric measurements, transverse diameter of the Michaelis sacral rhomboid area ≤9.6 cm, maternal height ≤ 155 cm, height to symphysio-fundal height ratio ≤4.7, lower limb length ≤78 cm, and head circumference to height ratio ≥ 35.05 with accuracy of 81.2%, 68.2%, 65.5%, 63.3%, and 61.5%, respectively, were better predictors. The best predictor was obtained by combination of maternal height ≤155 cm or the transverse diameter of the Michaelis sacral rhomboid area ≤9.6 cm and Johnson's formula estimated fetal weight ≥3255 g, with an accuracy of 90.5%, sensitivity of 70%, and specificity of 93.7%. CONCLUSIONS Combination of other anthropometric measurements and estimated fetal weight with maternal height in comparison to maternal height alone leads to a better predictor for dystocia.