Multiple pregnancy, breech and abnormal presentations

Published on 09/03/2015 by admin

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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.

Once full dilatation is reached, the breech must be allowed to descend to the perineum before an episiotomy is performed. As the breech is delivering, the sacrum is guided gently to the anterior position with the operator’s fingers and thumbs over the iliac crests and lumbar spine of the fetus, respectively, and the breech, legs and abdomen allowed to deliver spontaneously. The legs may need to be flexed to assist delivery (Pinard’s manoeuvre). Pushing is encouraged until the scapulae are visible and at this stage Lovset’s manoeuvre (rotation of the trunk) can be used to assist delivery of the shoulders and arms. Delivery of the head should be controlled manually (Mauriceau–Smellie–Veit manoeuvre) or by using forceps.

Regardless of the mode of delivery, breech presentation is associated with an increased perinatal morbidity and mortality, and, therefore, must be considered a high-risk pregnancy.

Transverse (and oblique) lie

The lie of the fetus is the relationship of the fetus to the long axis of the uterus. The lie is oblique if the head or buttocks are found in one or other iliac fossa, and the lie is transverse if they are found in the patient’s flanks. Unless these positions convert during pregnancy, vaginal delivery will not be possible and a caesarean section must be performed.

The aetiologies of both these presentations are similar to those outlined for breech presentation and also an ultrasound assessment should be performed for the same reasons (Fig. 13.2).

image

Figure 13.2 Fetal lie describes the relationship of the long axis of the fetus to the long axis of the uterus. (A) Transverse; (B) oblique; (C) longitudinal.

(Redrawn with permission from Symonds E M, Symonds I M 2003 Essential Obstetrics and Gynaecology, 4th edn. Edinburgh: Churchill Livingstone, p. 80.)

Management

Both transverse and oblique lie are uncommon at term and, if this is the case, the woman should be admitted for the remainder of her pregnancy for observation, as she is at high risk for cord prolapse if the membranes rupture from 37 to 38 weeks. If an identifying cause can be found on ultrasound scan, e.g. placenta praevia, then an elective caesarean section should be arranged. If no cause can be found, then the patient is observed until the lie stabilizes to cephalic for at least 48 hours, at which stage the labour can be induced.

A caesarean section for transverse lie can be technically difficult and should only be performed by an experienced obstetrician, especially if the fetal back is presenting and particularly so if there is oligohydramnios. This is because it is more difficult to access a fetal foot in order to perform a breech extraction. In this situation a general anaesthetic may be preferred (to allow more uterine relaxation). The other potential problem with a transverse lie is that the lower uterine segment is poorly developed and a vertical uterine incision may be required.

Cord prolapse

If the membranes rupture in the presence of a transverse or oblique lie then cord prolapse is likely and an immediate vaginal examination should be performed to exclude or confirm the prolapse. If the cord is found in the vagina then the woman should be placed in a knee–chest position or on all fours (with her buttocks higher than her head) to allow gravity to assist in avoiding cord compression against the pelvic cavity by the presenting part. The examiner’s hand should remain in the vagina, which will also assist in preventing cord compression until caesarean section can be performed. The examiner’s hand should not be withdrawn from the vagina until the surgeon has opened the uterus. An alternative strategy is to catheterize and fill the bladder to 500 ml, which may prevent the presenting part compressing the cord until caesarean section can be performed.

Multiple pregnancy

The incidence of twin pregnancy is approximately 1 in 100 and that of triplets is 1 in 1000, although the incidence of all multiple pregnancies is increasing because of increasing use of assisted conception techniques.

Aetiology of twin pregnancy

Twinning can be either mono- or dizygotic, referring to the number of maternal eggs used in fertilization.

Dizygotic twins are the commonest (60%) and result from the fertilization of two separate ova by separate sperm and are, therefore, no more genetically similar than siblings in the same family and may be of different sex. Monozygotic twins result from mitotic division of a single fertilized ova (zygote) into identical twins.

Therefore, dizygotic twins are always dichorionic and diamniotic, whereas monozygotic twins can share the same amnion and chorion depending on the stage at which the mitotic division occurred.

Predisposing factors include:

• Increasing maternal age and parity

• Family history

• Race

• Assisted conception (approximately 20% of all in vitro fertilization pregnancies).

Management

1. Diagnosis – women will often have exaggerated symptoms of pregnancy, including hyperemesis gravidarum. On examination the uterus feels larger than would be expected for her dates. Ultrasound assessment is usually performed in all pregnancies and should reveal the diagnosis.

2. Multiple pregnancy is not a normal pregnancy and should be closely monitored.

3. Both congenital abnormality and intrauterine growth restriction (IUGR) are more common in multiple pregnancy and so regular ultrasound assessment is important at 28, 32 and 36 weeks or more frequently if necessary.

4. An early ultrasound scan should determine chorionicity at 12 weeks or less.

Complications of multiple pregnancy

Maternal

• Hyperemesis often requiring admission for rehydration

• Miscarriage

• Pregnancy-induced hypertension and pre-eclampsia, which often presents earlier and is more aggressive than in singleton pregnancies

• Gestational diabetes

• Anaemia

• Antepartum and postpartum haemorrhage

• Placenta praevia

• Maternal discomfort.

Fetal

• Perinatal mortality is increased fourfold

• Congenital abnormality, especially in monozygotic twins

• Preterm labour occurs in 40% of twin pregnancies. More than 50% of babies from multiple pregnancies are less than 2500 grams compared with 6% of babies from singleton pregnancies

• Placental insufficiency or IUGR, especially in monochorionic twins

• Twin–twin transfusion in monochorionic twins, due to anastomosis of vessels within the single placental mass of a monochorionic twin pregnancy. In this condition one twin gains at the expense of the other, i.e. one twin becomes anaemic and the other polycythaemic

• Malpresentation of the first twin occurs in 20% of cases.

A twin delivery is high-risk, especially for the second twin. There may be added complications of preterm labour, malpresentation and postpartum haemorrhage. A plan for labour and delivery should be discussed antenatally with the consultant. A trial of vaginal delivery will generally be recommended if the first twin is cephalic and there are no added complications.

Delivery

The decision on mode of delivery depends on the presentation of the leading twin and on the presence of maternal or fetal complications. There is no evidence to suggest that caesarean section is advantageous if the first twin is cephalic, regardless of the presentation of the second twin. However, 50% of twins at term in spontaneous or induced labour will need caesarean delivery, usually because of fetal distress in the second twin. Caesarean section is indicated for all the usual reasons of a singleton pregnancy or if the first twin is breech or a transverse lie.

It is usual to induce labour for twins between 38 and 40 weeks and continuous monitoring of both twins throughout labour is essential as the fetuses, particularly the second twin, are at increased risk of hypoxia.

An epidural is recommended, as the second twin may need to be delivered by breech extraction. Labour is closely monitored and the first twin is delivered in the usual manner and the cord clamped and cut. The lie of the second twin is determined and presentation can be confirmed by ultrasound if necessary. If the lie is not longitudinal then external cephalic version can be used. Once the head or breech enters the pelvis the membranes are ruptured (often with fundal pressure) and pushing begins again. If contractions diminish, then an oxytocin drip is commenced. The second twin is then delivered in the usual manner, but breech extraction may be required if the second twin is not cephalic. The cord is double-clamped and cut, and the placenta is delivered. It is recommended that an oxytocin infusion is commenced as there is an increased risk of postpartum haemorrhage.

Complications

• Inefficient uterine action, especially after delivery of the leading twin

• Fetal distress, especially of the second twin

• Cord prolapse when rupturing membranes of second twin

• Locking is rare but can occur if leading twin is breech and the second twin is cephalic

• Postpartum haemorrhage

• Postpartum thrombosis.

Summary

• All women with a malpresentation should deliver in hospital.

• Breech presentation is associated with an increased perinatal mortality rate and, therefore, is considered a high-risk pregnancy.

• Transverse and oblique lie at term are uncommon and women should be admitted after 37 weeks as cord prolapse is more common in these situations and is an obstetric emergency.

• Multiple pregnancies have significantly increased fetal and maternal morbidity and mortality and, therefore, require regular specialist monitoring.

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