Brow Presentation

Brow presentation is a fetal head that is partly extended, between the vertex and the face, so that the brow (the area between the anterior fontanelle and the orbital ridges) presents at the pelvic inlet. It is the rarest of the malpresentations. It matters because the presenting diameter (mentovertical, about 13 cm) is the largest of the head, so vaginal birth is not possible with an average baby and obstructed labour follows if it persists.

• Risk factors: multiparity, contracted pelvis, large baby, prematurity, anencephaly, polyhydramnios, uterine anomaly.
• Many brows convert to vertex or face spontaneously during labour.
• Persistent brow needs caesarean section.

Labour is slow with a head that remains high and unengaged, and the cervix dilates poorly. Abdominal palpation shows a prominent head with both the occiput and sinciput at one level.

• Head high and not engaged at full dilatation.
• Fetal heart heard on the side of the chest.
• Differential diagnosis: face presentation, occiput posterior vertex, deflexed vertex, breech, hydrocephalus, anencephaly, cephalopelvic disproportion.
• Complications: obstructed labour, prolonged labour, uterine rupture, fetal distress, birth injury, facial bruising, caesarean section, cord prolapse, fistula.

The diagnosis is made by vaginal examination after the cervix has dilated, with ultrasound confirmation.

• Vaginal examination: anterior fontanelle at one side, the orbital ridges and root of the nose at the other, with the mouth and chin out of reach (to distinguish from face); the frontal suture runs in line.
• Abdominal palpation: a prominent head with the sinciput and the occiput at about a similar level.
• Ultrasound: partially extended head, neck angle, facial profile, presentation and lie.
• Cardiotocography; pelvis assessment; estimated fetal weight.

The principle is to wait a short time for conversion in a well mother and fetus, and to deliver by caesarean section if the brow persists.

• Supportive: continuous external cardiotocography; avoid scalp electrodes; Ringer's lactate 1 litre IV over 2 hours; empty the bladder; stop oxytocin; reassess 2-hourly; consent for caesarean section; paediatric team at birth.
• Pharmacological: cefazolin 2 g IV as a single dose before caesarean section; analgesia (epidural or pethidine 50 to 100 mg IM 4-hourly); oxytocin 10 IU IM after birth, then 20 IU in 1 litre Ringer's lactate at 125 mL per hour for 4 hours; tranexamic acid 1 g IV over 10 minutes if bleeding exceeds 500 mL; newborn vitamin K 1 mg IM.
• Procedures: caesarean section for persistent brow, with the head disimpacted by a hand in the vagina when deep; vaginal birth only for a preterm or very small baby, or after spontaneous conversion to face or vertex; no attempt at manual conversion, vacuum or forceps with a persistent brow.
• Special groups: a dead or anomalous fetus (anencephaly) allows vaginal birth after counselling, with destructive delivery by a trained operator if obstruction occurs; a uterine scar has a lower threshold for caesarean section.
• Red flags: head not engaging at full dilatation, bandl ring, abnormal fetal heart rate, cord prolapse, scar tenderness, maternal exhaustion.
• Follow-up: newborn facial bruising and swelling resolving in 3 to 7 days; examination for birth injury; bladder catheter for 24 hours after caesarean section; review at 6 weeks.