Postpartum fetal head circumference and its influence on labour duration in nullipara.

A retrospective analysis of postpartum fetal head circumference (FHC) and birth weight and its effect on the duration of labour was undertaken. The aim was to assess the predictive value of postpartum FHC versus birth weight in predicting dystocia. A FHC > 37 cm was associated significantly with a prolonged first and second stage of labour. A receiver operator curve (ROC) shows that the sensitivity and specificity of a FHC > 37 cm is as good as a fetal weight > 4.5 kg in predicting dystocia.