Multiple pregnancy, breech and abnormal presentations

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13 Multiple pregnancy, breech and abnormal presentations

Chapter Contents

Malpresentations215

Breech215
Transverse (and oblique) lie217

Multiple pregnancy219

Aetiology of twin pregnancy219
Management219
Complications of multiple pregnancy220
Delivery220

Summary221

Malpresentations

Breech

The presentation of the fetus refers to the part of the fetus that occupies the lower uterine segment, which in this case is the fetal buttocks. This is the commonest malpresentation, occurring in 3–4% of singleton pregnancies at term, but in up to 25% in preterm labour. There are three types of breech presentation (Fig. 13.1):

1. Frank breech – buttocks presenting with the legs extended.

2. Complete breech – legs flexed so that feet present beside the buttocks.

3. Footling breech – one or both feet presenting below the buttocks.

image

Figure 13.1 Breech presentations. (A) Extended (frank); (B) flexed (complete); (C) footling.

(Redrawn with permission from Rymer J, Davis G, Rodin A et al. 2003 Preparation and Revision for the DRCOG, 3rd edn. Edinburgh: Churchill Livingstone, p. 235.)

Aetiology

In most cases of breech presentation, no cause is found, but there are situations that predispose to this presentation.

Maternal causes:

• Grand multiparity results in uterine laxity so that the fetus has an increased likelihood of changing position

• Uterine abnormalities, e.g. bicornuate or septate

• Pelvic tumours or bony abnormalities that prevent engagement of the head

• Full bladder in labour.

Placental causes:

• Placenta praevia

• Oligo- or polyhydramnios.

Fetal causes:

• Multiple pregnancy

• Fetal abnormality

• Prematurity.

Investigations

Clinical examination is known to pick up only 50% of breeches at term but it may detect the presenting part as wider than normal and the harder head will be felt in the fundus of the uterus, which will be ballotable. An extended leg breech has the head in the midline compared to the flexed breech, where the head is more lateral. An ultrasound scan will confirm the diagnosis and determine the type of breech, the liquor volume, the placental site, the estimated fetal weight and the presence of a fetal abnormality. Despite this, approximately one-third are undiscovered until during labour.

Management

If a breech presentation is diagnosed antenatally women can be offered external cephalic version which has a 1% risk of cord accident or abruption. This is a method to manipulate the lie of the fetus into a cephalic presentation with the aid of tocolysis to relax the uterus. The procedure is successful in 40% of primiparous and 60% of multiparous patients if performed after 37 weeks. If the breech presentation persists, then a decision must be made about the mode of delivery, which remains controversial. Most obstetricians would now advocate an elective caesarean section for all persistent breech presentations at term. However, the multiparous patient with a breech may be offered the option of a vaginal delivery in the presence of a normal pelvis and an estimated fetal weight of 2500–3500 g.

Breech delivery is becoming less common, but is a skill that all obstetricians should be familiar with, as unexpected breech deliveries will always occur.

Vaginal delivery of the breech

Most practitioners would not induce a woman with a breech presentation, as the best chance for a successful vaginal delivery is spontaneous labour and, likewise, few would advocate augmentation for slow progress in labour. The fetus should be monitored continuously, often with the scalp electrode attached to the buttock, and epidural anaesthesia is advised.

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