Malpositions and malpresentations

Malpositions are abnormal positions of the vertex of the fetal head (with the occiput as the reference point) relative to the maternal pelvis. Malpresentations are all presentations of the fetus other than vertex.

PROBLEM

• The fetus is in an abnormal position or presentation that may result in prolonged or obstructed labour.

GENERAL MANAGEMENT

• Make a rapid evaluation of the general condition of the woman including vital signs (pulse, blood pressure, respiration, temperature).

• Assess fetal condition:

- Listen to the fetal heart rate immediately after a contraction:

- Count the fetal heart rate for a full minute at least once every 30 minutes during the active phase and every 5 minutes during the second stage;

- If there are fetal heart rate abnormalities (less than 100 or more than 180 beats per minute), suspect fetal distress.

- If the membranes have ruptured, note the colour of the draining amniotic fluid:

- Presence of thick meconium indicates the need for close monitoring and possible intervention for management of fetal distress;

- Absence of fluid draining after rupture of the membranes is an indication of reduced volume of amniotic fluid, which may be associated with fetal distress.

• Provide encouragement and supportive care.

• Review progress of labour using a partograph.

Note: Observe the woman closely. Malpresentations increase the risk for uterine rupture because of the potential for obstructed labour.

DIAGNOSIS

DETERMINE THE PRESENTING PART

• The most common presentation is the vertex of the fetal head. If the vertex is not the presenting part, see Table S-12.

• If the vertex is the presenting part, use landmarks of the fetal skull to determine the position of the fetal head (Fig S-9).

Figure S-9

 Landmarks of the fetal skull 

DETERMINE THE POSITION OF THE FETAL HEAD

• The fetal head normally engages in the maternal pelvis in an occiput transverse position, with the fetal occiput transverse in the maternal pelvis (Fig S-10).

• With descent, the fetal head rotates so that the fetal occiput is anterior in the maternal pelvis (Fig S-11). Failure of an occiput transverse position to rotate to an occiput anterior position should be managed as an occiput posterior position. 

• An additional feature of a normal presentation is a well-flexed vertex (Fig S-12), with the fetal occiput lower in the vagina than the sinciput.

• If the fetal head is well-flexed with occiput anterior or occiput transverse (in early labour), proceed with delivery.

• If the fetal head is not occiput anterior, identify and manage the malposition (Table S-11).

• If the fetal head is not the presenting part or the fetal head is not well-flexed, identify and manage the malpresentation (Table S-12).

TABLE S-11 Diagnosis of malpositions 

TABLE S-12 Diagnosis of malpresentations

MANAGEMENT

OCCIPUT POSTERIOR POSITIONS

Spontaneous rotation to the anterior position occurs in 90% of cases. Arrested labour may occur when the head does not rotate and/or descend. Delivery may be complicated by perineal tears or extension of an episiotomy.

• If there are signs of obstruction or the fetal heart rate is abnormal (less than 100 or more than 180 beats per minute) at any stage, deliver by caesarean section.

• If the membranes are intact, rupture the membranes with an amniotic hook or a Kocher clamp.

• If the cervix is not fully dilated and there are no signs of obstruction, augment labour with oxytocin.

• If the cervix is fully dilated but there is no descent in the expulsive phase, assess for signs of obstruction (Table S-10):

- If there are no signs of obstruction, augment labour with oxytocin.

• If the cervix is fully dilated and if:

- the fetal head is more than 3/5 palpable above the symphysis pubis or the leading bony edge of the head is above -2 station, perform caesarean section;

- the fetal head is between 1/5 and 3/5 above the symphysis pubis or the leading bony edge of the head is between 0 station and -2 station:

- Delivery by vacuum extraction and symphysiotomy;

- If the operator is not proficient in symphysiotomy, perform caesarean section;

- the head is not more than 1/5 above the symphysis pubis or the leading bony edge of the fetal head is at 0 station, deliver by vacuum extraction or forceps.

BROW PRESENTATION

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.

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

• 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.

Do not deliver brow presentation by vacuum extraction, outlet forceps or symphysiotomy. 

FACE PRESENTATION

The chin serves as the reference point in describing the position of the head. It is necessary to distinguish only chin-anterior positions in which the chin is anterior in relation to the maternal pelvis (Fig S-24 A) from chin-posterior positions (Fig S-24 B). 

Figure S-24

 Face presentation

Prolonged labour is common. Descent and delivery of the head by flexion may occur in the chin-anterior position. In the chin-posterior position, however, the fully extended head is blocked by the sacrum. This prevents descent and labour is arrested.

CHIN-ANTERIOR POSITION

• If the cervix is fully dilated:

- Allow to proceed with normal childbirth;

- If there is slow progress and no sign of obstruction (Table S-10), augment labour with oxytocin;

- If descent is unsatisfactory, deliver by forceps.

• If the cervix is not fully dilated and there are no signs of obstruction, augment labour with oxytocin. Review progress as with vertex presentation. 

CHIN-POSTERIOR POSITION

• If the cervix is fully dilated, deliver by caesarean section.

• If the cervix is not fully dilated, monitor descent, rotation and progress. If there are signs of obstruction, deliver by caesarean section.

• If the fetus is dead:

- Deliver by craniotomy;

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

Do not perform vacuum extraction for face presentation. 

COMPOUND PRESENTATION

Spontaneous delivery can occur only when the fetus is very small or dead and macerated. Arrested labour occurs in the expulsive stage.

• Replacement of the prolapsed arm is sometimes possible:

- Assist the woman to assume the knee-chest position (Fig S-25);

- Push the arm above the pelvic brim and hold it there until a contraction pushes the head into the pelvis. 

- Proceed with management for normal childbirth.

Figure S-25

Knee-chest position 

• If the procedure fails or if the cord prolapses, deliver by caesarean section.

BREECH PRESENTATION

Prolonged labour with breech presentation is an indication for urgent caesarean section. Failure of labour to progress must be considered a sign of possible disproportion (Table S-10)

The frequency of breech presentation is high in preterm labour. 

EARLY LABOUR

Ideally, every breech delivery should take place in a hospital with surgical capability.

• Attempt external version if:

- breech presentation is present at or after 37 weeks (before 37 weeks, a successful version is more likely to spontaneously revert back to breech presentation);

- vaginal delivery is possible;

- membranes are intact and amniotic fluid is adequate;

- there are no complications (e.g. fetal growth restriction, uterine bleeding, previous caesarean delivery, fetal abnormalities, twin pregnancy, hypertension, fetal death).

• If external version is successful, proceed with normal childbirth.

• If external version fails, proceed with vaginal breech delivery (see below) or caesarean section.

VAGINAL BREECH DELIVERY

• A vaginal breech delivery by a skilled health care provider is safe and feasible under the following conditions:

- complete (Fig S-20) or frank breech (Fig S-21);

- adequate clinical pelvimetry;

- fetus is not too large;

- no previous caesarean section for cephalopelvic disproportion;

- flexed head.

• Examine the woman regularly and record progress on a partograph.

• If the membranes rupture, examine the woman immediately to exclude cord prolapse. 

Note: Do not rupture the membranes.

• If the cord prolapses and delivery is not imminent, deliver by caesarean section.

• If there are fetal heart rate abnormalities (less than 100 or more than 180 beats per minute) or prolonged labour, deliver by caesarean section.

Note: Meconium is common with breech labour and is not a sign of fetal distress if the fetal heart rate is normal.

The woman should not push until the cervix is fully dilated. Full dilatation should be confirmed by vaginal examination. 

CAESAREAN SECTION FOR BREECH PRESENTATION

• A caesarean section  is safer than vaginal breech delivery and recommended in cases of:

- double footling breech;

- small or malformed pelvis;

- very large fetus;

- previous caesarean section for cephalopelvic disproportion;

- hyperextended or deflexed head.

Note: Elective caesarean section does not improve the outcome in preterm breech delivery.

COMPLICATIONS

Fetal complications of breech presentation include: 

• cord prolapse;

• birth trauma as a result of extended arm or head, incomplete dilatation of the cervix or cephalopelvic disproportion;

• asphyxia from cord prolapse, cord compression, placental detachment or arrested head;

• damage to abdominal organs;

• broken neck.

TRANSVERSE LIE AND SHOULDER PRESENTATION

• If the woman is in early labour and the membranes are intact, attempt external version:

- If external version is successful, proceed with normal childbirth;

- If external version fails or is not advisable, deliver by caesarean section (page P-43).

• Monitor for signs of cord prolapse. If the cord prolapses and delivery is not imminent, deliver by caesarean section.

Note: Ruptured uterus may occur if the woman is left unattended .

In modern practice, persistent transverse lie in labour is delivered by caesarean section whether the fetus is alive or dead.

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