Assisted vaginal delivery and shoulder dystocia

Chapter 16 Assisted vaginal delivery and shoulder dystocia

David T Y. Liu, Mentor: George S H. Yeo

CHAPTER CONTANTS

Indications for instrumental assisted vaginal deliveries 127

Maternal indications 127

Fetal indications 128

Labour indications 128

Requirements for assisted delivery 128

Forces operating in the second stage of labour 128

Passage and passenger 128

Uterine contractions 128

Maternal expulsive effort 128

Fundal pressure 128

Assisted delivery 129

Informed consent 129

Instruments for assisted delivery 129

Vacuum extractors 129

Choosing between forceps and vacuum extraction for assisted deliveries 129

Traction procedures 132

Before application of instruments 132

During the use of instruments 132

Delivery of the baby 133

Procedures after delivery 133

Maternal complications 139

Neonatal complications 139

Medicolegal issues 139

Symphysiotomy 140

Precautions 140

Shoulder dystocia 140

Intrapartum 141

Post partum 141

Bladder function and care during labour and after delivery 141

After delivery 142

INDICATIONS FOR INSTRUMENTAL ASSISTED VAGINAL DELIVERIES

The incidence of instrumental vaginal delivery should be between 8% and 10% of births.

Maternal indications

• Maternal exhaustion.

• To avoid excessive voluntary expulsive effort when increase in intra-abdominal, intrathoracic and intracranial pressure is best avoided (e.g. maternal cardiac disease, poor respiratory reserves, or neurological disorders).

Fetal indications

• Fetal distress when there is good reserve and little calculated difficulty for assisted delivery.

• For the aftercoming head of the breech (by controlled delivery with forceps).

REQUIREMENTS FOR ASSISTED DELIVERY

1. Thorough assessment of:

a. the forces of the second stage of labour, in particular presence of dystocia

b. the degree of difficulty of the assisted delivery.

2. The fetus – membranes are ruptured. The head is engaged (determined by abdominal palpation and vaginal examination). Position of the fetal head is defined and the station is at or below the ischial spines. The fetus’s ears are always palpable to provide guidance for position of fetal head.

3. The mother – the cervix is fully dilated. There is adequate anaesthesia. Absolute disproportion is excluded.

4. Adequate communication between the woman, her partner and medical carers. Obtain informed consent.

5. The obstetrician is experienced or supervised by an experienced senior. There must be willingness to abandon the attempt if assisted delivery does not proceed easily. Ensure neonatal support and caesarean section facilities are available.

FORCES OPERATING IN THE SECOND STAGE OF LABOUR

Successful outcome for assisted delivery is governed by a dynamic balance between the passage, passenger and powers.

Passage and passenger

An accurate assessment of the passage and passenger begins with antenatal care and continues into the intrapartum period.

In the antenatal period, the fetus (or passenger) is continuously monitored for signs of intrauterine growth restriction or macrosomia. Fetal size, presentation, position, attitude and growth are assessed by a combination of abdominal and ultrasound examination.

The passage is assessed by clinical examination and magnetic resonance and radiological pelvimetry. Gross pelvic contracture can be detected, but usefulness of pelvimetry for predicting dystocia has been questioned.

Past obstetric history detailing modes of delivery for various birthweights allows estimation of fetal size against past performances to indicate likelihood of dystocia in the current pregnancy.

Gross cephalopelvic disproportion must be excluded before any attempt at assisted vaginal delivery. Minor degrees of disproportion are difficult to detect. Possible reduced pelvic diameters and/or a moderately big fetus forewarn likely borderline cephalopelvic disproportion and need for assistance.

Powers

Abdominal palpation and tocographic monitoring both detect frequency and duration of uterine contractions but not their intensity. Use of intrauterine pressure catheters for intensity of uterine contractions is not helpful in the management of dystocia.

The forces in the second stage for delivery are:

• uterine contractions

• maternal expulsive effort

• fundal pressure.

Uterine contractions

Uterine contractions will facilitate assisted delivery.

Maternal expulsive effort

Poor maternal effort is a common indication for assisted deliveries. Pushing is both exhausting and ineffective when it is not synchronised with uterine contractions Advise women to push to coincide with uterine contractions. They should rest between contractions to avoid getting tired.

Fundal pressure

Fundal pressure is used during caesarean births and assisted deliveries (see Figure 16.1). Pressure is applied at the uterine fundus (usually over the buttocks of the fetus) along its longitudinal axis to coincide with uterine contractions and maternal expulsive efforts. Fundal pressure should not be applied in between contractions particularly when maternal effort is absent.

Figure 16.1 Application of fundal pressure: both hands are placed on the fundus of the uterus and a gentle push is applied during contraction.

ASSISTED DELIVERY

Assistance should be in synchrony with expulsive forces to overcome soft tissue resistance in the second stage of labour, usually for delivery of the fetal head. Resistance arises from individual difference in pelvic musculo-fascial soft tissue, perineal tissue compliance and to some degree moulding of the fetal head.

Informed consent

Assisted vaginal delivery is an operative procedure with attendant risks and complications, and therefore requires detailed discussion with the woman and her partner. Consent, usually verbal, is often obtained just before an emergency procedure from a distressed woman. Although necessarily brief, discussion and counselling are essential. A more detailed discussion should follow to debrief and answer questions.

Instruments for assisted delivery

Forceps

• Traction forceps

• Long handles, e.g. Neville Barnes

• Short handles for outlet procedures or during caesarean section, e.g. Wrigley’s

• Rotational forceps, e.g. Kjelland’s.

Description of forceps

Each forceps has a left and right fenestrated blade. Each traction blade has a cephalic curve for the fetal head and a pelvic curve to accommodate the curvature of the maternal pelvis. When joined as a pair through a fixed lock, these blades form a protective cage which surrounds the fetal head without compression. When traction is applied, pressure transmitted to the fetus is safely contained by the firm fetal malar bones (Figures 16.2, 16.3).

Figure 16.2 Large and small traction forceps (a) as separates, (b) as pairs and (c) applied.

Figure 16.3 Traction forceps illustrating (a) handle (b) shoulder, (c) lock, (d) shank, (e) blade with cephalic curve and (f) pelvic curve.

Kjelland’s rotational forceps differs from traction forceps. The shank is long and the blade is thin. The modest pelvic curve allows rotation through a much smaller circumference. The sliding lock allows application when asynclitism is present (see Chapter 19). Knobs on the handles point towards the occiput (also known as occipital knobs) (Figures 16.4–16.6).

Figure 16.4 Kjelland’s forceps (a) as separates and (b) as paired.

Figure 16.5 Components of Kjelland’s forceps: (a) handle, (b) shoulder, (c) sliding lock, (d) shank and (e) blade.

Figure 16.6 Rotation of Kjelland’s forceps (b) is through a smaller circumference than with the traction forceps (a).

Choosing between forceps and vacuum extraction for assisted deliveries

Contemporary reviews found that vacuum extraction was associated with significantly less maternal trauma than forceps delivery. Fewer caesarean sections were carried out in vacuum extractor groups. However, the vacuum extractor was associated with an increase in neonatal cephalhaematoma and retinal haemorrhages. Forceps were associated with a lower failure rate. The chief disadvantage of forceps is a higher risk of significant maternal perineal injury, especially anal sphincter injuries.

Neither instrument is superior for assisted vaginal deliveries. The forces and requirements for either form of assisted delivery are similar. The choice of instrument depends on the clinical scenario as well as the operator’s experience, training and preferences. Both instruments are equally suited to most assisted deliveries. In circumstances where cephalopelvic disproportion is confidently excluded and speed is of essence (e.g. ominous cardiotocographic tracing), forceps may be the instrument of choice for expediting delivery. The vacuum extractor may be preferred where asynclitism is present, when rotational delivery is needed and there is limited experience with forceps. There is no increased morbidity in completing a delivery by forceps when the vacuum fails provided that the requirements for assisted delivery are fulfilled. Table 16.1 shows a comparison between the two types of instrumental delivery. The long-term outcome is the same for mother and child.

Table 16.1 Instrumental vaginal delivery

	Forceps	Vacuum
Popularity	Decreased	Increased
Preterm	Yes	Not before 36 weeks
Undilated cervix (around 9 cm)	Contraindicated	Yes
Anaesthesia	Yes	Need less
Failure to achieve delivery	Less likely	More likely
Tissue trauma	Possible	Less
Cephalhaematoma	Possible	More likely
Retinal haemorrhage	Possible	More likely
Postpartum perineal pain	Yes	Less

TRACTION PROCEDURES

Box 16.1 describes the types of traction procedure used in assisted delivery.

Box 16.1 Traction procedures used in assisted delivery

American College of Obstetricians and Gynecologists (ACOG) classification of forceps deliveries 2000

Outlet procedure refers to the application of the instrument when:

• scalp is visible at the introitus without separating labia

• fetal skull has reached pelvic floor

• sagittal suture is in anteroposterior diameter, or in the right or left occiput anterior or posterior position

• fetal head is at or on perineum

• rotation is less than 45°

Low procedure refers to the application of the instrument when:

• the leading point of fetal skull is at station +2 or more, and not on the pelvic floor. There are two subdivisions:

rotation of 45° or less

rotation of more than 45°

Mid-pelvic procedure refers to the application of the instrument when:

• the head is engaged but the station is between 0 and +2.

• with subdivisions as for low procedures.

Before application of instruments

• Indication and requirements – ensure that these have been met.

• Communication with colleagues – inform consultant (if appropriate), anaesthetist and operating theatre staff (if a trial of forceps in operating theatre is indicated), and neonatologist (especially if the indication is for fetal distress).

• Informed consent – obtain verbal consent after explaining to the woman and her partner the need for assisted delivery. Caution the woman that intense pressure and the sensation of pelvic separation may be felt at the moment of birth. This is the normal experience of childbirth. Unless forewarned, especially in a nulliparous woman, this frightening sensation could be wrongly attributed to the misuse of instruments or obstetric ineptitude.

• Position – the lithotomy position is favoured. The legs are suspended by stirrups or other means. Adopt a 15° left lateral tilt to overcome supine hypotension.

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Tags: Labour Ward Manual

Mar 16, 2017 | Posted by admin in NURSING | Comments Off

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