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

Powers 128

Uterine contractions 128

Maternal expulsive effort 128

Fundal pressure 128

Assisted delivery 129

Informed consent 129

Instruments for assisted delivery 129

Forceps 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

Rotational procedures 135

Requirements 136

Manual rotation 136

Technique 136

Ventouse rotation 136

Technique 136

Rotation by Kjelland’s forceps 137

Application by wandering anterior blade 137

Application by the direct method 137

Rotation and delivery 137

Inherent dangers of Kjelland’s forceps 138

Trial of forceps or vacuum 138

Maternal complications 139

Neonatal complications 139

Medicolegal issues 139

Symphysiotomy 140

Precautions 140

Shoulder dystocia 140

Management 140

Antenatal 140

Intrapartum 141

Post partum 141

Haematomas 141

Bladder function and care during labour and after delivery 141

In labour 142

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).

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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).

Labour indications

• Malposition (e.g. occipitoposterior and occipitotransverse).

• Prolonged second stage of labour (1 hour for multiparas, 2 hours for nullipara). Extra hour with regional anaesthesia.

• To expedite delivery.

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.

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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).

Vacuum extractors

Rigid cups in use are:

• Malmstrom – anterior cup

• Bird – anterior and posterior cup

• O’Neill – anterior and posterior cup

• Mityvac – anterior cup

• Kiwi OmniCup – universal anterior and posterior cup

Soft cups in use are:

• Silc cup – anterior cup

• Silastic cup – anterior cup

Description of vacuum extractor

The principal components of the vacuum extractor are the pump, the pressure gauge, the traction piece and the cup used to raise the chignon for traction (Figure 16.7). Figure 16.8 shows a contemporary ventouse extraction and delivery system.

Figure 16.7 Components of the ventouse extractor: (a) pump, (b) container with pressure gauge, (c) traction piece and (d) cup.

Figure 16.8 (a) Contemporary ventouse extractor. (b) Vacuum delivery system.

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.

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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

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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.

• Bladder – empty the bladder to avoid damage during traction and/or rotation.

During the use of instruments

1. Position of the obstetrician – the flexed forearm is at the level of the vulva or slightly lower (Figure 16.9).

2. Position of the mother – the perineum should slightly overhang the edge of the bed. There should be room below the buttock for assisted delivery, especially for rotational forceps.

3. Check the instrument. For forceps delivery check that both blades lock easily and are well lubricated. For vacuum assisted delivery: check that the traction chain and the tubings are airtight; check that the suction apparatus and the vacuum have been connected properly; and choose the appropriate cup size (the largest cup possible should be used).

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4. Reassure the woman and her partner. Discourage pushing during insertion of the blades. The partner’s prime role is support and not as a spectator.

5. Apply the instrument as described in Box 16.2.

6. Check application.

Figure 16.9 Position of an obstetrician for forceps delivery. The woman’s legs are suspended by stirrups or other means.

Box 16.2 Application of instruments

Forceps

1. Insert the left blade first

a. Check that there is no uterine contraction and that woman is not pushing.

b. Place the index and middle fingers of the right hand along the left side of the fetal head to exclude the vaginal walls (Figure 16.10).

c. The left hand holds the blade vertical and by dropping the handles slips the forceps into position guided by the palmar aspects of the intravaginal fingers.

d. The blade rests over the fetal ear and malar bones.

2. Repeat the procedure for the right blade.

a. The right hand now holds the blades which are guided into position by the left index and middle fingers.

b. The blades should fall together into position.

3. If resistance is felt, check to ensure that all the requirements for forceps delivery are met.

4. Lock the two blades – no undue force should be used. If the blades do not lock easily reassess situation. The blades are then reapplied.

Vacuum

1) Lubricate the cup.

2) Insert it sideways through the introitus (Figure 16.11). Aim to position the centre of the cup 3 cm anterior to the posterior fontanelle and over the sagittal suture. This will maintain the head in the optimal maximum flex attitude. Avoid placement over fontanelle.

3) Exclude cervix or folds of vaginal mucosa.

4) Create an initial vacuum up to 0.2 kPa over 1–2 minutes. Check again that cervix and vaginal mucosa have been excluded from the cup.

5) The vacuum pressure is raised to a working pressure of 0.8 kPa.

6) Once working pressure is achieved wait for 30 seconds for the chignon to form before applying traction (Figure 16.12).

Figure 16.10 Application of traction forceps.

Figure 16.11 Insertion (a) and application (b) of cups.

Figure 16.12 (a) Formation of a chignon to assist traction (b) with residue swelling persisting for 24–48 hours after cup is removed.

For forceps

• Ensure that the sagittal suture is in the midline, equidistant between the blades (Figure 16.13).

• The posterior fontanelle should be one finger’s breadth above the shanks (for occipitoanterior position).

• The fenestrated blades should admit one finger between the heel of the blade and the fetal head.

Figure 16.13 Position of sagittal suture with correct application of forceps.

For vacuum

• Ensure that the centre of the cup is over the sagittal suture and 3 cm anterior to the posterior fontanelle.

• Check that the woman’s cervical and vaginal mucosa have been excluded from the cup before traction.

• Apply gentle traction. The vacuum cup is held against the fetal head with the thumb and index finger of the left hand to detect any tendency of the cup to separate. Check repeatedly with index finger to detect inclusion of cervix and vagina into the vacuum.

• Apply traction during uterine contractions and bearing down efforts in line with the pelvic axis (Figure 16.14). Pajot’s manoeuvre may be used with the forceps. Traction is applied perpendicular to the cup in the direction of the pelvic axis when the vacuum is used (Figure 16.15).

• No more than 15–20 kg of pull is required to achieve delivery.

• Apply traction for 20–30 seconds at a time. Delivery should be achieved with three or fewer pulls (Figure 16.16). More than 30 minutes of vacuum can result in scalp necrosis.

• An episiotomy is usually required as the vertex is crowning.

• Change direction of traction to 30° from the horizontal once the vertex (chin in face presentation) emerges beneath the symphysis. Failure to change direction is an important cause of trauma to the perineum (Figures 16.16, 16.17).

• After crowning ask mother to stop pushing and start panting. Panting will produce gentle intermittent intra-abdominal pressure which nudges the baby slowly out of the birth canal.

Figure 16.14 Traction in line with pelvic axis.

Figure 16.15 (a) Placement of intravaginal fingers and (b) direction of traction.

Figure 16.16 Delivery of head with forceps.

Figure 16.17 Delivery of the head with the Ventouse extractor.

Delivery of the baby

1. Deliver the head slowly to avoid tears to the perineum or extension of the episiotomy.

2. Once the head is delivered, the blades of the forceps are disengaged (or the vacuum is released and the cup removed)

The rest of the delivery is the same as that for normal birth.

Procedures after delivery

1. Check arterial and venous cord pH and base excess.

2. Examine the pelvic structures to exclude damage. Locate the apex of the episiotomy to check for extension. Rotational deliveries are more likely to cause damage.

3. Jointly with the neonatologist conduct examination of the baby (including any soft tissue injuries). Communicate findings of the baby to the parents and reassure if appropriate.

4. Document fully findings, discussions with the mother and her partner, steps of the procedure and condition of the mother and baby after delivery (including Apgar score and cord pH).

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ROTATIONAL PROCEDURES

A wider diameter is presented when the vertex is in the occipitolateral or occipitoposterior position. Rotation into the anteroposterior diameter of the pelvic outlet may occur on the perineum or at any level between the ischial spines and the perineum. Delivery in the occipitoposterior position may increase perineal trauma unless carefully conducted.

The three most common techniques used for placing the vertex into the anteroposterior diameter of the pelvic outlet are:

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• rotation by hand (manual)

• rotation with a vacuum extractor

• rotation with Kjelland’s forceps.

Requirements

• Include requirements for assisted vaginal deliveries. Ensure adequate anaesthesia at level of rotation.

• A neonatologist should be in attendance.

• If any difficulty is anticipated, the procedure should be conducted in the operating theatre with provisions made for immediate caesarean section.

Manual rotation

This is a safe technique. Pressure on the fetal head is easy to judge and trauma to soft tissue is less likely. Check cervical dilatation and adequacy of pelvis.

Technique

1. Confirm the malposition.

2. Lubricate the traction forceps and place them within reach.

3. The left hand is used for right occipitolateral or posterior positions, the right hand is used for left occipitolateral or posterior positions.

4. Insert the hand into the vagina to grasp the fetal head across the parietal diameters with thumb uppermost. Use thumb, index and middle finger if access is limited (Figure 16.18).

5. Disimpact the fetal head and rotate the occiput anteriorly. Place the free hand over the woman’s abdomen in the region of the anterior fetal shoulder. The shoulder is brought across the midline towards the opposite iliac crest to assist rotation at the same time as rotation of the vertex. An assistant can help prevent tendency of the shoulder to revert to its original position. Flexion with contraction is often evident with correct rotation.

6. While the vertex is held in the occipitoanterior position, the forceps blades are applied in the usual manner. Check correct alignment of the sagittal suture.

7. Difficulties in locking the blades suggest inadequate rotation and hence incorrect application of the forceps.

8. Apply traction only after application of the forceps is judged to be correct.

Figure 16.18 Position of hand for manual rotation.

Ventouse rotation

Technique

1. Apply the cup well back on the fetal head so that traction corrects any deflexion which is usual in malposition.

2. Asynclitism (see Chapter 19) is almost always present in malposition and is corrected by a more posterior application of the cup.

3. Initial traction down towards the floor allows the vertex to descend and correct asynclitism. Rotation usually takes place at the pelvic floor level. The thumb and index finger in the vagina to ensure contact between cup and the scalp can also help rotation by directing cup in direction of turn.

4. After successful rotation, complete the delivery by maintaining traction perpendicular to the cup in line with the pelvic axis.

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Rotation by Kjelland’s forceps

Designed for rotation, the shank is long and the blade thin. There is no pelvic curve so rotation is through a smaller circumference. The sliding locks allow application when asynclitism is present (see Figures 16.5, 16.6).

Application by wandering anterior blade

1. Check placement of the blades by assembling them in front of the pelvis. Ensure that the directional knobs point towards the occiput.

2. Select the anterior blade (the blade which will be placed on the upper surface of the fetal head). The second and third fingers of the hand on the side of the fetal face are inserted into the vagina (Figure 16.19).

3. The anterior blade, held vertically by the free hand, is slipped into the vagina between the fetal face and the intravaginal fingers. The handle is depressed towards the floor at the same time. The face is chosen because the bitemporal diameter, being smaller than the biparietal diameter, provides for easier application.

4. When the blade is two-thirds of the way inside the vagina, the handle is nearly horizontal. The handle is rotated towards the floor from this position while the intravaginal fingers assist the passage of the blade across the fetal face. When the blade is positioned correctly over the ear and malar bone the handle is raised so that the blade will encompass the full length of the fetal head (Figure 16.20).

5. Sometime, the occiput rotates into the direct occipitoposterior position during the application of the wandering blade. Kjelland’s forceps can then be inserted directly with the knobs pointing towards the occiput.

6. If difficulty is encountered, withdrawing the blade by a short distance can help. Alternatively, apply the blade across the occiput.

Figure 16.19 Application of anterior blade.

Figure 16.20 Direction of blade over fetal face by intravaginal fingers.

Application by the direct method

1. The anterior blade is held vertically with the handle pointing towards the floor. The cephalic curve is placed in contact with the fetal head at the level of the ears and malar bones. Two intravaginal fingers guide placement of the blade as the handle is elevated.

2. The posterior blade is always applied directly to the head. Intravaginal fingers guide the blade into position. The tip of the blade is always kept close to the fetal head. When applied correctly there should be no difficulty in locking the blades. Presence of asynclitism would mean that the shoulders of the handles are not at the same level.

Rotation and delivery

1. When correctly applied, the handles are at 45° from the horizontal and in line with the pelvic axis. Vertical direction of the handles more than 45° indicates that the head is not fully engaged and it may be safer to abandon the procedure.

2. Correct asynclitism by adjusting the handles so that the shoulders of the blades are level. Sometimes this is easier during a contraction.

3. The blades are held by the shoulders. The fourth finger is interposed between the handles to remind the obstetrician not to compress them. This particular grip for rotation prevents excessive force being used and is highly sensitive to the presence of unnecessary resistance (Figure 16.21).

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4. The fetal head is rotated at the level of application of the forceps. The rotational force needed is usually not more than what is comfortably applied with two fingers. If difficulty is encountered, rotation may be achieved with descent during the next contraction. Occasionally moving the fetal head up a few centimetres allows rotation at the widest pelvic plain.

5. Once rotation is achieved, the grip is changed to facilitate traction (Figure 16.22). Traction must be along the pelvic axis (Figure 16.23). Interpose the thumb between the handles. Pajot’s manoeuvre can help (Figure 16.24).

6. An episiotomy is made in the usual manner. Do not make an episiotomy before rotation otherwise the spiral torque during rotation may cause extension of the episiotomy.

Figure 16.21 Grip technique for rotation.

Figure 16.22 Grip technique for traction.

Figure 16.23 Axis traction.

Figure 16.24 Axis traction with Pajot’s manoeuvre to maintain traction in pelvic axis.

Inherent dangers of Kjelland’s forceps

There are two inherent dangers in the design of the Kjelland’s forceps. Firstly, the thin blades can cause considerable soft tissue trauma. Secondly, the wandering technique necessitates moving the blades over a large area of vagina. This increases the risk of trauma. Whether Kjelland’s forceps should continue to be used is controversial.

Trial of forceps or vacuum

• All potentially difficult forceps or vacuum deliveries should be conducted as a trial by an experienced obstetrician.

• The trial should be conducted in the operating theatre with immediate access to caesarean section if the trial fails (remember prophylactic citrates, informed consent, intravenous line and grouped blood available at short notice). The neonatologist, anaesthetist and theatre staff must be in attendance. Do not perform episiotomy until vaginal delivery is assured.

• The trial fails when there is no advance or little descent with a moderate amount of traction. A trial of forceps after use of vacuum should only be performed if the operator is confident vaginal delivery is possible and the fetal head is deeply engaged. Only then is delivery accomplished without harm to the mother or baby. Note reason for failure with the first instrument. Check requirements for assisted delivery are met.

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• Leave an indwelling catheter, disimpact the fetal head and place it above the level of ischial spines to facilitate delivery of the head by caesarean section when trial of vaginal delivery fails.

MATERNAL COMPLICATIONS

Assisted vaginal delivery is associated with the following maternal complications:

• Perineal and vaginal lacerations, extension of episiotomy, third degree tears and haematoma formation. A thorough examination must be performed after delivery is achieved. Injury to the urethral-vesical angle and anal sphincter can lead to immediate problems such as difficulty with voiding or subsequent urinary and faecal incontinence.

• Vaginal haematoma formation and laceration can occur with spontaneous vaginal deliveries but are more likely after rotational instrument delivery. Severe laceration, particularly if the vaginal vault is involved, may require laparotomy and extended surgery hence an experienced obstetrician must be present. Haematomas following rupture of vaginal veins will need evacuation if large, painful or judged to be enlarging.

• Do not perform instrumental delivery unless the cervix is fully dilated. Exceptions include vacuum delivery for the second twin or when there is a need for urgent vaginal delivery at 9 cm cervical dilatation and requirements for easy delivery are met. Torn cervix leading to maternal death has been reported with use of the vacuum. Again experience is mandatory before attempting repair of cervical lacerations especially if there is extension into the fornix. Minor lacerations that are not bleeding can be managed expectantly.

• The lumbosacral nerves may be impinged upon by movement of the sacroiliac joints, compression by the fetal presenting part or use of forceps. Transient loss of sensory and motor function may result.

Following delivery:

• Consider thromboprophylaxis if there are risks for thrombosis.

• Debrief with woman. Ensure adequate analgesia and urinary output for 24 hours.

• There is a place for antibiotics.

NEONATAL COMPLICATIONS

Assisted vaginal delivery is associated with the following neonatal complications:

• Risk of perinatal trauma in instrumental vaginal delivery correlates with duration of attempt, level of the fetal head in the birth canal, need for rotation and condition of baby at start of procedure.

• Compared with forceps, the vacuum is associated with higher rates of neonatal trauma. These include cephalhaematoma with neonatal hyperbilirubinaemia needing phototherapy, scalp injuries and retinal haemorrhage.

• Chignon or swelling of the scalp, which develops when vacuum is applied, is seen when the cup is removed. This swelling, which diffuses within an hour to behave like a normal caput succedaneum, usually disappears over 1 or 2 days. Scalp markings or abrasions can last as long as 6 months after delivery.

• Subcutaneous haematomas resolve in a few days. Cephalhaematomas may take up to a few weeks to disappear. Reassure the parents.

• Neonatal jaundice is more common after vacuum extraction than after forceps or spontaneous delivery. There is no difference in the number of babies requiring phototherapy.

• Subgaleal haemorrhage associated with difficult instrumental delivery is more likely when fetal hypoxia or coagulopathy is present. This life-threatening condition is a serious complication associated with vacuum extraction. Intracranial haemorrhage can also complicate difficult vacuum extractions.

• Retinal haemorrhage, more common after instrumental delivery than normal birth, is significantly more likely after vacuum extraction than after forceps delivery. This is a transient lesion.

MEDICoLEGAL ISSUES

Instrumental vaginal delivery followed by complications or poor fetal outcome is a ready situation for complaints and litigation. The following are important from the perspective of clinical governance and risk management:

• Appropriate assessment of the situation. Obstetric history, presence of maternal or fetal compromise, good appreciation of pelvic diameters and configurations, the woman’s preference, available expertise and option for caesarean section are all important issues.

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• The obstetrician must be adequately trained or supervised.

• The woman and her partner must be made aware of need, likely outcome and options. Obtain consent and maintain communication to inform and reassure.

• There is no place for instrumental delivery if the obstetrician cannot properly assess the pelvis and relate fetal head size to pelvic diameters and outlet.

• Be prepared to abandon the procedure when difficulty is encountered and when there is little descent with traction. Avoid repeated attempts and use of multiple instruments. Forceps can be considered after failure with the vacuum. The reverse sequence is not acceptable. Sequential use of instruments increase neonatal trauma.

• Detail documentation is essential. This includes indication, discussion with the woman and her partner regarding risks and options, any complication and remedial action, condition of mother and baby, cord arterial and venous values.

• Full explanation and prompt attention to complications. Offer apology where appropriate.

• Introduce audit for individual obstetrician and the labour ward as a whole to ensure continuous quality control.

SYMPHYSIOTOMY

This procedure is seldom used but can be effective for delivery if the aftercoming head of a normal live breech is stuck at the pelvic outlet. Requirements are:

• Lithotomy position.

• General, regional or local anaesthesia.

• Catheterised bladder. Leave catheter indwelling.

• Incise the skin above symphysis with a firm blade. Probe with the blade to identify non-bony joint.

• Displace the urethra from the midline by a finger in the vagina.

• Hold the blade at 30° from horizontal and advance vertically down towards the vagina. Use a sawing action until the tip of the blade is sensed by the intravaginal finger.

• Once the joint separates apply forceps and deliver the fetal head. An episiotomy is helpful.

Precautions

• Avoid wide separation of symphysis to protect sacroiliac joint and urethra.

• Insert drain if there is venous bleeding when arcuate ligaments are cut.

• Leave catheter in situ for 48 hours.

• Support pelvic girdle and nurse the mother on her side.

SHOULDER DYSTOCIA

The term shoulder dystocia describes difficulty with delivery of the shoulder after delivery of the fetal head. This unpredictable emergency occurs in 0.5–2% of vaginal deliveries. The complication is usually due to the anterior shoulder becoming stuck above the symphysis pubis (unilateral dystocia). Bilateral dystocia is when both shoulders are impacted above the pelvic inlet. Shoulder dystocia results from failure of the shoulder to rotate to the transverse diameter of the pelvic inlet followed by 90° rotation to the anteroposterior diameter of the outlet.

Risk factors include:

• Abnormalities of fetal chest or abdomen.

• Fetal macrosomia – the rate increases from 10% to 20% for birthweight between 4250 gm and 4750 gm.

• Diabetic women – the risk compared with non-diabetic women is increased by more than 70% for similar birthweight.

• Prolonged labour and long second stage. (70% are associated with normal labours.)

• Past history of shoulder dystocia. (Over 50% incidence of shoulder dystocia are in babies weighing less than 4000 gm.)

• Suspect when fetus descends with contractions than retracts between contractions (Turtle’s sign) or if the fetal head extension is restricted during delivery.

Management

Antenatal

• Neither clinical nor ultrasound diagnosis of macrosomia is reliable.

• No evidence that induction at full term is helpful but benefit of earlier delivery at 37–38 weeks remains a subject for investigation.

• There is a place for elective caesarean section when estimated fetal weight is more than 4500 gm, when likely macrosomia accompanies diabetes and for a definite history of previous difficulty with shoulder dystocia.

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• Forewarn at risk women to ensure their delivery is in hospital. Document clearly to alert labour ward staff.

Intrapartum

All labour ward medical staff must be regularly ‘drilled’ to become practised in managing this emergency. Assess all women admitted for delivery. If risk is suspected make sure an experienced obstetrician attends delivery. When this emergency arises activate the following steps.

1. Recruit help from an experienced midwife, a senior obstetrician, an anaesthetist and a paediatrician.

2. Adopt McRoberts’ manoeuvre. Flex the woman’s thighs against abdomen and chest. Offer assistance if she cannot do this herself. The manoeuvre straightens the lumbosacral angle and rotates the symphysis superiorly thus opening the pelvic outlet. This manoeuvre alone is effective in resolving 80% of this emergency. The posterior shoulder is often pushed over the sacral promontory into hollow of the sacrum.

3. The left lateral position is seldom used. Squatting or knee chest ‘on all fours’ position achieves the same advantages but delivery in this position requires experience.

4. Perform an episiotomy to remove soft tissue resistance and allow better access for subsequent steps.

5. Apply suprapubic pressure with flat of hand to free the shoulder, to adduct and reduce the biacromial diameter and direct the shoulder beneath the symphysis into the anteroposterior widest diameter of the pelvic outlet. This step improves delivery rate by an additional 3%.

6. If delivery is not achieved adopt Woods cork screw manoeuvre. Insert appropriate hand into posterior vagina and rotate posterior shoulder clockwise or anticlockwise 180°. This will bring the impacted anterior shoulder to below the level of the symphysis to allow delivery.

7. If the above steps fail employ Mazzanati’s procedure to deliver the posterior arm. Flex arm at the elbow. The hand or forearm is grasped and swept across the baby’s chest and face. The anterior shoulder is disimpacted and slides out beneath the symphysis. The baby’s clavicle or humerus may be fractured (18% risk). The biacromial diameter can be reduced by breaking the clavicle (clavicular osteotomy).

8. Impaction of both anterior shoulder against the symphysis and the posterior shoulder in the sacral promontory necessitate resort to Zavanelli’s option. Rotate baby’s head into the anteroposterior position. Flex the head and push it into the pelvis. Deliver by caesarean section. Maternal morbidity must be considered.

Points to remember

• If one manoeuvre fails move quickly to the next to avoid delay.

• Brachial plexus injury follows excessive or prolonged traction to the baby’s neck, e.g. Erb’s palsy.

• Keep detailed records of all procedures and outcomes.

Post partum

• Enlist the neonatologist’s assistance. Check for presence of injury to baby and mother.

• When appropriate discuss events with the woman and her partner to answer questions and agree plans for future pregnancies.

HAEMATOMAS

A shearing action between the vagina and deeper tissues during normal, assisted or rotational delivery can rupture the vaginal plexus of veins to form a haematoma. If extensive, this will involve the paravaginal space, the labia, urethra and even extension into the broad ligament. Inadequate haemostasis following episiotomy repair or closure of the caesarean section wound also result in haematoma formation.

• Presents as pain, bruising, urinary retention and, if extensive, hypovolaemic consequences.

• Vaginal examination and if indicated ultrasound scan will help diagnosis.

• Small haematomas can be managed conservatively. Catheterisation is required if the urethra is involved.

• For large haematomas an experienced obstetrician must attend to assess the situation. Surgery, on occasion laparotomy, may be required to evacuate the clots and secure haemostasis. Transfusion may be necessary. Leave drains after surgery if oozing is anticipated.

BLADDER FUNCTION AND CARE DURING LABOUR AND AFTER DELIVERY

Labour and particularly delivery can potentially affect pelvic floor musculature and nerves causing urinary and bowel dysfunction. Contributory factors include nulliparity, prolonged labour, epidural anaesthesia with bladder overdistension, instrumental delivery and vaginal or perinatal trauma.

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In labour

• Encourage voiding every 3 or 4 hours.

• If unable to void obtain consent and intermittently catheterise. Record output.

• Normal bladder capacity is 300–500 ml. A residual volume of more than 700 ml will warrant urological follow-up.

• Following delivery ensure women are advised about the importance of bladder function and care.

After delivery

• Make sure women can void before leaving the labour ward. Communicate bladder function and care to postnatal carers.

• Prevention of urinary retention is part of good labour care.

• Indwelling catheter until the woman is ambulatory may be necessary after assisted delivery. Seek the woman’s consent and offer clear explanation.

• If voiding difficulties persist, intermittent self-catheterisation is the current usual advice.

References

American College of Obstetricians and Gynecologists 2000 Operative vaginal delivery: use of forceps and vacuum extractors for operative vaginal delivery. ACOG Practice Bulletin Number 17, Washington DC

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