Occipito posterior position

Brow presentation

BackgroundBrow presentation is the least common of all fetal presentations. Early in labor, a brow presentation may be encountered, but this is often unstable, and it converts to a vertex presentation. Occasionally, extension may result in a face presentation. The causes of a persistent brow presentation are generally similar to those causing a face presentation. These include cephalopelvic disproportion or pelvic contracture and increasing parity and prematurity, which are implicated in more than 60% of cases of persistent brow presentation. Premature rupture of membranes preceded brow presentation in as many as 27% of cases. Definition

BROW PRESENTATION is caused by partial extension of the fetal head so that the occiput is higher than the sinciput

In a brow presentation, the fetal head is partaially extended with the frontal bone, which is bounded by the anterior fontanelle and the orbital ridges, lying at the pelvic brim. The presenting diameter of 13.5 cm is the mentovertical, which exceeds all diameters in average-size pelvis. Incidence: 0.02% of singleton deliveries or Approximately 1 in 1000 deliveries.Causes : Similar to Face Presentation

Diagnosis .

On abdominal examination, more than half the fetal head is above the symphysis pubis and the occiput is palpable at a higher level than the sinciput.

On vaginal examination, the presenting part is high and may be difficult to reach. The anterior fontanelle may be felt on one side of the pelvis and the orbital ridges, and possibly the root of the nose, at the other.Management

In brow presentation, engagement is usually impossible and arrested labour is common. Spontaneous conversion to either vertex presentation or face presentation can rarely occur, particularly when the fetus is small or when there is fetal death with maceration. It is unusual for spontaneous conversion to occur with an average-sized live fetus once the membranes have ruptured.

1. Ceserean section required in most cases

2. Brow presentation rarely can deliver vaginally unless:

Spontaneously converts to vertex or Face Presentation Fetus is very small or pelvis is very large

3. If the fetus is alive, deliver by caesarean section.

4. If the fetus is dead and:

the cervix is not fully dilated, deliver by caesarean section;

the cervix is fully dilated, Deliver by craniotomy;

If the operator is not proficient in craniotomy, deliver by caesarean section.

5. Do not attempt to convert brow presentation to vertex

6. Avoid Oxytocin7. Do not deliver brow presentation by vacuum extraction, outlet forceps or symphysiotomy.Mechanism of Labor

Three labor courses are possible when the fetal head engages in a brow presentation. The brow may convert to a vertex presentation, convert to a face presentation, or remain as a persistent brow presentation. The earlier in labor the diagnosis is made, the more likely conversion is to occur. Vertex or face presentation labor courses are managed accordingly when spontaneous conversion occurs.

In the brow presentation, the occipitomental diameter, which is the largest diameter of the fetal head, is the presenting portion. The head engages but can descend only with significant molding. This molding and subsequent caput succedaneum over the forehead can become so extensive that identification of the brow by palpation is impossible late in labor, which may result in a missed diagnosis in a patient who presents later in active labor.

Descent and internal rotation occur with an adequate pelvis and if the face can fit under the pubic arch. The persistent brow presentation with subsequent delivery only occurs in cases of a large pelvis and/or a small infant. At any time during labor, a brow presentation may convert to a face or vertex presentation.