Malpresentation, malposition, and cephalopelvic disproportion
Normal labour involves an appropriate-sized fetus in a vertex presentation with a well-flexed head that descends and rotates within the maternal pelvis in response to uterine contractions, delivering in an occipitoanterior position. Abnormal labour occurs when any one or a combination of these factors deviates from normal. It may involve a malpresentation (e.g. face, brow, or breech), a malposition (e.g. occipitoposterior), or cephalopelvic disproportion. The consequences include prolonged labour, obstructed labour, operative vaginal delivery, or caesarean section. Appropriate management requires expertise in clinical assessment, decision-making, and the technical and non-technical skills of operative delivery. A systematic approach is required including an awareness of risk factors for abnormal labour, early identification of deviations from normal, use of preventative strategies where possible, and appropriate intervention when necessary. Good teamwork and clear communication between midwives and obstetricians is essential within a labour ward setting. Timely transfer may be required in a homebirth setting. Particular skills are required in low-resource settings where obstructed labour may be advanced at the time of presentation.