Brow presentation: when the baby's forehead leads in labour

For a baby to pass through the pelvis easily, the chin is usually tucked in so the smallest part of the head leads. In a brow presentation the head is held half way between this flexed position and a fully extended one. Patient.info describes the fetal head as staying between full extension and full flexion so that its biggest diameter, called the mento-vertex, presents.

The forehead, or brow, is therefore the leading part. It is classed with face presentation as a malpresentation, meaning any presentation other than the vertex. GPnotebook notes that the position can be corrected, either by the head flexing to a vertex position or extending to a face presentation, so the head may move as labour proceeds.

Patient.info says brow presentation occurs in 0.14 percent of deliveries, which equates to roughly 1 in 700, while GPnotebook says it occurs approximately once in 1,000 deliveries. Either way it is very uncommon.

The sources reviewed for this page list general risk factors for malpresentation, including prematurity, multiple pregnancy, uterine abnormalities such as fibroids, an abnormal baby, placenta praevia and a first pregnancy, but they do not identify causes that are specific to brow presentation.

The diagnosis is made on vaginal examination during labour. Patient.info says that brow presentation is usually only diagnosed once labour is well established, with the anterior fontanelle and the supra-orbital ridges palpable. GPnotebook describes it as being identified by feeling the orbital ridges.

It cannot usually be spotted by the woman and is not routinely identified before labour begins. If it is suspected, an obstetrician is called to examine, and the team reviews the baby's heart rate pattern and the progress of labour together.

GPnotebook states that, in this position, the presenting diameter is too large, about 13.5 cm on average, for the baby to be delivered, and Patient.info says that unless the head flexes, a vaginal delivery is not possible and a caesarean section is required.

By comparison, GPnotebook puts the presenting diameter in a face presentation at about 9.5 cm, which is why a face presentation, with the chin forward, can sometimes deliver vaginally whereas a persistent brow presentation cannot.

Once the diagnosis is made, the plan depends on whether the head changes position. GPnotebook says the position can be corrected, either by flexing to vertex or extending to face, with caesarean section as the other alternative. If the head flexes into a vertex position, labour can continue as usual. If it extends to a face presentation, the considerations are those of a face presentation, which depend on the direction of the chin.

NICE's intrapartum guideline lists any non-cephalic presentation among the reasons to transfer to obstetric-led care, which is the setting where an obstetrician can reassess you and a caesarean can be arranged if needed.

If the position persists, or if labour is not progressing or the baby shows signs of distress, the team will recommend a caesarean section. The NHS explains that a caesarean may be recommended when labour is not progressing or the baby is not getting enough oxygen and nutrients, and in some of those cases the baby may need to be delivered immediately.

• Labour is monitored closely, with the baby's heart rate checked regularly or continuously.

• The obstetrician will examine again to see whether the head has flexed or extended.

• You will be given the reasons for any recommendation and asked for your consent.

The NHS says most caesareans are carried out under spinal or epidural anaesthetic, the operation normally takes about 40 to 50 minutes, and women who have no complications can usually go home 1 to 2 days later. You will be offered painkillers, and the NHS advises taking things easy at first and avoiding some activities, such as driving, until the postnatal check-up at 6 weeks.

A woman who has had a caesarean for a brow presentation will normally be able to discuss options for later pregnancies, including the chance of a vaginal birth after caesarean and what the birth would involve.

Brow presentation is a variation in how the head enters the pelvis rather than an illness of the baby. The sources reviewed describe how it is managed but do not provide outcome statistics, so this page does not give figures for complications. When it is recognised promptly and the birth is managed in a unit with obstetric and neonatal support, the aim is a safe birth for both mother and baby.

If you feel distressed after an emergency birth, tell your midwife, health visitor or GP. Many units offer a chance to go through what happened with a member of the team.

Because a brow presentation is found during labour, it is managed by the obstetric team in whichever hospital you are giving birth. If you have chosen private care, it is reasonable to ask how an unexpected malpresentation, a caesarean in labour and neonatal support would be arranged.