Face and Brow Presentation
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Direct answer
Face and brow presentations are malpositions of the fetal head in which the head is extended, so the presenting part is the face or brow instead of the vertex. The mentum determines the outcome, with a mentoanterior face often delivering vaginally, while a mentoposterior face and brow presentation usually need caesarean. Diagnosis is by vaginal examination of the orbital ridges, malar bones and mouth, supported by ultrasound.
What you must remember
- Face presentation: extension of the head so the presenting part lies between the orbital ridges and the chin, the mentum.
- Brow presentation: partial extension, with the presenting part between the orbital ridge and the anterior fontanelle, which is often non-progressive.
- Mentoanterior: chin anterior, with a reasonable chance of vaginal delivery when the pelvis is adequate.
- Mentoposterior: chin posterior, often with prolonged labour and caesarean delivery.
- Brow presentation: caesarean is usually required, as the presenting diameter is too large for vaginal birth.
- Causes: anencephaly, prematurity, multiparity, polyhydramnios, fetal macrosomia, pelvic contraction and fetal goitre.
- Instrumental delivery: vacuum is contraindicated in face presentation, and forceps are reserved for a mentoanterior face by an experienced operator.
A comparison of outcomes by chin position
A 30-year-old in labour is found to have a face presentation with the chin to the back. The table links each presentation to its usual mode of delivery, so the plan can be made from the vaginal examination and ultrasound.
| Presentation | Chin position | Usual mode of delivery |
|---|---|---|
| Face | Mentoanterior | Vaginal delivery possible if the pelvis is adequate |
| Face | Mentoposterior | Often caesarean, or delivery after rotation |
| Brow | Not applicable | Usually caesarean |
A mentoanterior face is a good presentation for vaginal birth, while a mentoposterior chin rarely rotates in labour. Brow presentation may convert to a face or vertex, but the outcome in labour is seldom vaginal.
Diagnosis should be confirmed by vaginal examination in labour and reconfirmed by ultrasound if the presentation is unclear. Neonatal teams should be alerted, because facial swelling and bruising are common after a face presentation. Caesarean timing is decided with the obstetric team and the woman's wishes once the chin position is clear.
Where the exam tries to catch you
Face and brow questions test whether the candidate uses the chin position, rather than the presentation name alone, to choose the delivery route.
- Trap: "Face presentation always needs caesarean." Correct: a mentoanterior face can deliver vaginally when the pelvis and fetus allow.
- Trap: "Apply vacuum to a face presentation to hasten delivery." Correct: vacuum is contraindicated, and forceps are reserved for a mentoanterior face, because traction risks injury to the fetal face and neck.
- Trap: "Brow presentation is a normal vertex presentation in labour." Correct: brow is a malposition with a larger presenting diameter, so caesarean is usually needed.
Frequently asked questions
What determines the mode of delivery in face presentation?
The position of the mentum determines the mode of delivery in face presentation, with a mentoanterior chin allowing vaginal delivery when the pelvis is adequate. A mentoposterior chin is less likely to deliver vaginally, so caesarean is often needed.
How is face presentation diagnosed?
Face presentation is diagnosed on vaginal examination by feeling the orbital ridges, malar bones, nose, mouth and chin, and ultrasound can confirm the position. Face and vertex can be confused without careful palpation, so the examiner should identify the chin deliberately.
Why is brow presentation usually delivered by caesarean?
Brow presentation is usually delivered by caesarean because the presenting diameter is larger than the vertex, so vaginal delivery is unlikely. Spontaneous conversion to a face or vertex presentation can occur in labour, which is why the plan should be reviewed.
What causes face and brow presentation?
Face and brow presentations are linked to anencephaly, prematurity, multiparity, polyhydramnios, fetal macrosomia and pelvic contraction. Identifying the cause helps predict whether the malposition will persist.