Retention of the after-coming head refers to the rare situation in which there is difficulty in extracting the fetal head during vaginal breech delivery (Fig. 4.1). The incidence of breech presentation in labour varies according to gestational age, from about 23 % at 28 weeks to 3–4 % at term. The latter incidence depends also on local practices for the promotion of external cephalic version. The number of vaginal breech deliveries complicated by retention of the after-coming head is largely dependent on local policies of case selection for elective caesarean section. Footling or knee presentations, fetuses with estimated birth weights above 3800 g or below 1500 g and those with extended heads are common indications for caesarean section, but criteria may vary between centres. Some studies report retention of the after-coming head to occur in as much as 10 % of vaginal breeches, but the criteria used for the diagnosis are questionable.

Moulding of the fetal head to the birth canal is frequent during the course of labour in cephalic presentations, but there is little time for this to occur in breeches. In preterm fetuses head-to-pelvis ratios are higher, and this may allow the fetal pelvis to pass through an incompletely dilated cervix, while the head is later retained.

The risk factors for retention of the after-coming head are displayed in Table 4.1 and are mainly related to fetal head dimensions, flexion of the fetal neck and dimensions of the maternal pelvis. An extended fetal neck predisposes to retention because it increases the anteroposterior diameter of the head.

Currently, these risk factors are used mainly to select cases where elective caesarean section is proposed as the preferential mode of delivery, but in some centres this is proposed to all women with breech presentations at term or in labour.

Independently of these practices, healthcare professionals need to maintain competence in management of retention of the after-coming head, because they may always encounter it unexpectedly, particularly when women present in advanced labour with the breech already delivering.

The main complication of fetal head retention is acute hypoxia/acidosis, due to umbilical cord compression between the fetal head and the surrounding maternal tissues, while the airway is still not in contact with air. Additional complications may arise from iatrogenic trauma caused by attempts to resolve the situation.

Perinatal mortality in some series reaches 4–8 % and is mainly due to hypoxia/acidosis and intracranial haemorrhage, but it is also related to the increased risk of malformations associated with breech presentation at term. Perinatal morbidity includes hypoxic-ischaemic encephalopathy; dislocation or fracture of cervical vertebrae; stretching/lacerations of the brachial-cephalic plexus and cervical muscles; dislocation of the lower jaw; fracture of the femur, humerus and clavicle; rupture of abdominal organs (spleen, liver, kidney, suprarenal glands); external genital lesions; meconium aspiration syndrome; infection; and neonatal sepsis.

Little is known about how long head retention may last before perinatal death or long-term injury occur. The situation providing the closest parallel for comparison is shoulder dystocia with coexisting nuchal cords (Chap. 3). Although there are no absolute certainties, less than 5 min of sustained cord compression is unlikely to put the fetus at risk, while a 5–9 min interval appears to be associated with mild short-term neurological dysfunction and full recovery, and more than 12 min causes substantial risk of permanent damage. These timings require adaptation when fetal oxygenation is previously compromised and when there is fetal growth restriction. Because of sustained cord occlusion, umbilical blood gas values may not reflect the severity of hypoxia/acidosis, and the occurrence of hypoxic-ischaemic encephalopathy will be the best predictor of long-term outcome.

Retention of the after-coming head is established after there have been two or three unsuccessful attempts to extract the fetal head in a vaginal breech delivery. The most commonly used methods for this extraction are the Mauriceau-Smellie-Veit and the Bracht manoeuvres (see below).