After studying this chapter you should be able to:
Knowledge criteria
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Outline the mechanism of spontaneous vaginal delivery
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Describe the aetiology, diagnosis and management of the common malpresentations and malpositions in labour
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Define the different types on perineal trauma
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Describe indications, methods and complications of vaginal delivery and caesarean section
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List the risk factors and initial steps in management of shoulder dystocia
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Describe the complications in the third stage of labour including postpartum haemorrhage, perineal trauma, haematoma, amniotic fluid embolism
Clinical competencies
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Conduct a normal vaginal delivery
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Carry out an episiotomy repair on a practic mannequin
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Explain the procedures of caesarean section and instrumental delivery
Professional skills and attitudes
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Consider the importance of choice of mode of delivery in partnership with the mother and respect the views of other healthcare workers
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Consider the emotional implications for woman, family and staff of birth
Normal vaginal delivery
Normal vaginal delivery marks the end of the second stage of labour.
The second stage of labour is defined as the period from the time of complete cervical dilatation to the baby’s birth. It is convenient to consider the second stage in two phases: the descent in the pelvis, i.e. the pelvic or ‘passive’ phase, and the perineal or ‘active’ phase of the second stage. During the descent phase the mother does not normally experience the sensation of bearing down and, from a management point of view, this phase may be regarded as an extension of the first stage of the labour. In the perineal phase the urge to bear down is present although this may be masked or diminished if epidural analgesia has been provided for the woman. Therefore, unless the head is visible with contractions, the dilatation of the cervix and the station of the presenting part should be confirmed by vaginal examination before encouraging the woman to bear down.
Provided there are no adverse clinical factors present, a normal duration of the second stage is commonly regarded as lasting up to 2 hours in the nulliparous woman and 1 hour in the multipara. If the woman has received epidural analgesia, these times are extended by 1 hour for each group respectively. Progress in the second stage is monitored by descent of the fetal head assessed by an abdominal and vaginal examination. The fetal head is considered to be engaged when, no more than one-fifth of the head is palpable abdominally and the bony part of the vertex has descended to the level of the ischial spines.
If the labour is normal, women may choose a variety of positions for delivery but the supine position should be discouraged because of the risk of supine hypotensive syndrome. Many women adopt a semi-reclining position which has the advantage of reducing the risk of supine hypotension and is a suitable position for assisted delivery or perineal repair should these procedures be required.
Normal vaginal delivery Women should be guided by their own urge to push. Pushing effort should allow for an unhurried, gentle delivery of the fetal head and this can be achieved by combining short pushing spells with periods of panting, thus giving the vaginal and perineal tissues time to relax and stretch over the advancing head ( Fig. 12.1 ). Several contractions may occur before the head crowns and is delivered. For the delivery of the head, either the ‘hands on’ technique – supporting the perineum and flexing the baby’s head – or the ‘hands poised’ method – with the hands off the perineum but in readiness – can be used to facilitate spontaneous birth.
Episiotomy is not routinely required for spontaneous vaginal birth but may be indicated if the perineum begins to tear, if the perineal resistance prevents delivery of the head or if concern for the wellbeing of the fetus requires that the birth be expedited. Where an episiotomy is performed, the recommended technique is a mediolateral incision originating at the vaginal fourchette and directed usually to the mother’s right side ( Fig. 12.2 ).
With the next contraction, the head is gently pulled downwards along the longitudinal axis of the baby until the anterior shoulder is delivered under the sub-pubic arch and then the baby is pulled anteriorly to deliver the posterior shoulder and the remainder of the trunk.
The infant will normally cry immediately after birth but if breathing is delayed the nasopharynx should be aspirated and the baby’s lungs inflated with oxygen using a face mask. If the onset of breathing is further delayed, intubation and ventilation may become necessary. The condition of the baby is assessed at 1 and 5 minutes using the Apgar scoring system ( Table 12.1 ) and again at 10 minutes if the baby is depressed. If the baby is born in poor condition (Apgar score at 1 minute is 5 or less), the cord should be double-clamped for paired cord blood gas analysis.
| 0 | 1 | 2 | |
|---|---|---|---|
| Colour | White | Blue | Pink |
| Tone | Flaccid | Rigid | Normal |
| Pulse | Impalpable | <100 beats/min | >100 beats/min |
| Respiration | Absent | Irregular | Regular |
| Response | Absent | Poor | Normal |
Management of the third stage
Active management of the third stage of labour is recommended, which includes the administration of oxytocin (10 I/U) intramuscularly to the mother, followed by late clamping (>2 minutes) and cutting of the cord. When the signs of placental separation are seen, i.e. the lengthening of the cord, trickle of blood and the uterus becoming globular and hard due to contraction and extruding the placenta into the lower segment, the placenta is delivered by controlled cord traction, a method commonly referred to as the Brandt-Andrews technique ( Fig. 12.3 ).
Repair of episiotomy or perineal injury
A careful examination of the mother’s perineum should be made as soon as possible to identify the degree of perineal or genital tract trauma sustained during the birth. Perineal trauma caused either by episiotomy or tearing may be classified as first, second, third or fourth-degree tears. A first degree tear describes laceration to vaginal and perineal skin only. A second-degree tear involves the posterior vaginal wall and underlying perineal muscles but not the anal sphincter. Third-degree injury to the perineum is damage that involves the anal sphincter complex, and a fourth-degree laceration is injury to the perineum that includes the ano/rectal mucosa.
In the case of a first-degree perineal tear, there is no need for suturing if the skin edges are already apposed provided the wound is not bleeding. Episiotomies and second-degree lacerations should be sutured to minimize bleeding and to expedite healing. Third and fourth-degree perineal lacerations should be repaired under epidural/spinal or general anaesthesia by an experienced surgeon in an operating theatre under good lighting conditions. This is discussed in more detail in the next section.
Episiotomy repair For episiotomy repair, the woman should be placed in the lithotomy position so that a good view of the extent of the wound can be obtained ( Fig. 12.4 ). Repair should only be undertaken with effective analgesia in place using either local anaesthetic agent infiltration or epidural or spinal anaesthesia. Closure of the vaginal wound requires a clear view of the apex of the incision. It is recommended that an absorbable synthetic suture material be used for the repair using a continuous technique for the vaginal wall and muscle layer and a continuous subcuticular technique for the skin.
On completion of the procedure it is important to ensure that the vagina is not constricted and that it can admit two fingers easily. In addition, a rectal examination should be performed to confirm that none of the sutures has penetrated the rectal mucosa. If this occurs, the suture must be removed as it may otherwise result in the formation of a rectovaginal fistula.
Accurate repair of an episiotomy is important. Over-vigorous suturing of the wound or shortening of the vagina may result in dyspareunia and sexual disharmony with the partner. Failure to recognize and repair damage to the anal sphincter may result in varying degrees of incontinence of flatus and faeces.
Third and fourth degree injuries
Obstetric anal sphincter injuries are a complication of vaginal deliveries and lead to long-term sequelae : anal incontinence (up to 25%), perineal discomfort, dyspareunia (up to 10%) and rarely rectovaginal fistulas. A third degree tear is a partial or complete disruption of the external and internal sphincter; either or both of these may be involved. These tears are often subclassified as:
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3a: less than 50% of the external sphincter is disrupted
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3b: more than 50% of the external sphincter is disrupted
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3c: both the external and internal sphincter are disrupted.
A number of risk factors have been identified, though their value in prediction or prevention of sphincter injury is limited ( Box 12.1 ). It is important to examine a perineal injury carefully after delivery so as not to miss sphincter damage. This may increase the rate of sphincter damage, but it will help to reduce the rate of long-term morbidity.
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Large baby (>4 kg)
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First vaginal delivery
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Instrumental delivery (forceps > ventouse)
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Occipitoposterior position
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Prolonged Second stage
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Induced labour
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Epidural anaesthesia
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Shoulder dystocia
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Midline episiotomy
Repair and management of third and fourth degree tears
An experienced obstetrician should be performing or supervizing the repair. Good exposure, lighting and anaesthesia are prerequisites. The procedure should be covered with broad spectrum antibiotics and an oral regime carried on for at least 5 days following the repair. There are two recognized forms of repair that include the end-to-end method and overlapping of the sphincter ends. Documentation describing the extent of the tear, the method of repair as well as the level of supervision is vital. Immediately after the repair, the women should be debriefed, referred for physiotherapy and stool softeners should be prescribed. At the 6 week postnatal appointment, women need to be specifically asked about control of faeces, flatus, bowel movements as well as urgency and sexual dysfunction. An elective caesarean section for subsequent deliveries should be offered to all women who have sustained a sphincter injury if they remain symptomatic. Early referral to a colorectal surgeon is advised if physiotherapy has not relieved her symptoms.
Malpresentations
More than 95% of fetuses present with the vertex and are termed ‘normal’. Those presenting with other parts of the body (breech, face, brow, shoulder, cord) to the lower segment and cervix are known as malpresentations. There may be a reason for malpresentation, although in most instances there is no identifiable cause. They also present with specific problems in labour and during delivery. In modern obstetrics the presentation needs to be diagnosed early in labour and appropriate management instituted to prevent maternal or fetal injury.
Breech presentation is discussed in Chapter 8 .
Face presentation
In face presentation the fetal head is hyperextended so that the part of the head between the chin and orbits, i.e. the eyes, nose and mouth, that can be felt with the examining finger is the presenting part. The incidence is about 1 in 500 deliveries. In most cases the cause is unknown, but is associated with high parity and fetal anomaly particularly anencephaly. In modern obstetric practice where most pregnant women have an ultrasound scan for fetal abnormalities it is rare to see such conditions as a cause of face presentation.
Diagnosis
Face presentation is rarely diagnosed antenatally, but is usually identified during labour by vaginal examination when the cervix is sufficiently dilated to allow palpation of the characteristic facial features. However, oedema may develop that may obscure these landmarks. If in doubt, ultrasound will confirm or exclude the diagnosis. The position of a face presentation is defined with the chin as the denominator and is therefore recorded as mentoanterior, mentotransverse and mentoposterior ( Fig. 12.5 ).
Management
If the position is mento-anterior progress can be followed normally with the expectation of spontaneous vaginal delivery. However, if progress is abnormally slow it is preferable to proceed to caesarean section. In cases of persistent mentoposterior positions, vaginal delivery is not possible without manual or forceps rotation. Because the risk associated with these manoeuvres to the mother and infant is considerable, most obstetricians will perform a caesarean delivery.
Brow presentation
A brow presentation is described when the attitude of the fetal head is midway between a flexed vertex and face presentation ( Fig. 12.6 ) and is the most unfavourable of all cephalic presentations. The condition is rare and occurs in 1 in 1500 births. If the head becomes impacted as a brow the presenting diameter, the mentovertical diameter (13 cm), is incompatible with vaginal delivery.
