Labor dystocia

• Definition. Abnormal or inadequate progress in labor (see Chapter 61).
• Also known as failure to progress, prolonged labor, failure of cervical dilation, failure of descent of the fetal head.
• Causes. Inadequate “power” (uterine contractions), inadequate “passage” (bony pelvis), or abnormalities of the “passenger” (fetal macrosomia, hydrocephalus, malpresentation, extreme extension or asynclitism (lateral tilting) of the fetal head).
• Cephalopelvic disproportion (CPD) is classified as absolute (where the disparity between the size of the bony pelvis and the fetal head precludes vaginal delivery even under optimal conditions) or relative (where fetal malposition, asynclitism, or extension of the fetal head prevents delivery). Absolute CPD is an absolute contraindication to attempted vaginal delivery.
• Management. Exclude absolute CPD. Confirm “adequate” uterine activity (see Chapter 60). If contractions are “adequate,” one of two events will occur: dilation and effacement of the cervix with descent of the head, or worsening caput succedaneum (scalp edema) and molding (overlapping of the skull bones). Proceed with timely cesarean section delivery, if indicated.

Malpresentation