Prepared participatory childbirth

In this approach the parents undertake childbirth training, learning about the processes of childbirth and how to accept the pains of uterine contractions (see pp. 49–50). Labour is managed by trained staff, and the principles mentioned earlier are observed by both staff and patients. The birth takes place in a quiet environment and the baby is given to the mother at once so that she may offer suckling and celebrate the birth.

Women can have a prepared participatory childbirth in a normal hospital delivery room, but for some it is more satisfactory if there is a birthing centre.

Actively managed childbirth

The development of the partogram and the appreciation that most women have delivered within 12 hours of admission to hospital has led to another approach: actively managed labour.

On admission to the delivery unit, the diagnosis of labour is either confirmed or rejected. If the woman is in labour, the time of admission is designated as the start of labour. A partogram is started and the progress of labour is marked on it (Fig. 8.1). Vaginal examinations are made every 2–4 hours and the cervical dilatation is recorded on the partogram. Action lines, printed on transparent plastic, are superimposed on the partogram (Fig. 8.2). In the active stage of labour the slowest acceptable rate of cervical dilatation is 1 cm/h. If the cervical dilatation lies to the right of the appropriate action line the membranes are ruptured and an incremental dilute oxytocin infusion is established in nulliparous women (and some multiparous women), provided that a single fetus presents as a vertex and there are no signs of fetal distress.

Fig. 8.1 A partogram.

Fig. 8.2 Action lines for the partogram (Studd stencil). The lines show the slowest acceptable rate of cervical dilatation, commencing with the degree of dilatation on admission to the delivery unit.

Progress in the second stage of labour is judged by the descent of the fetal head and its rotation. One hour is allowed for the fetal head to reach the pelvic floor (the first or passive phase) and a further hour for the birth to be completed (the second or active phase). If there is delay in the passive phase then oxytocic augmentation is instituted. Delay in the active phase dictates close fetal monitoring and, where indicated, an operative vaginal delivery. Proponents of actively managed labour claim that the incidence of a labour lasting more than 12 hours is less than 3%; the caesarean section rate is 7–12% and the forceps rate is 8%. Opponents point out that only three randomized studies have been carried out, and that in these studies there was no reduction in the caesarean section or forceps rate.

Elective caesarean section

A small but increasing number of women, particularly those over the age of 35, inform their obstetrician during pregnancy that they wish to be delivered by caesarean section. The obstetrician should listen to the woman and discern the underlying reasons for her request. For some it may be a fear of the pain of labour, for others to avoid any risk of pelvic floor damage during delivery, or a perception that abdominal delivery removes all risks for the baby. It is particularly important that the risks of caesarean versus vaginal delivery are carefully explained (Box 8.3). If the woman confirms that she wishes to be delivered by caesarean section, the obstetrician should either agree to her wish or arrange for a consultation with another colleague.

Home birth

Women choosing this type of delivery must receive good prenatal care; must be screened for any medical or obstetric abnormality; must accept transferral to a hospital if an abnormality arises during pregnancy or childbirth; and must have an experienced midwife. Even then home birth is less safe than giving birth in a midwife-controlled birthing centre.

False labour

As term approaches many women complain of painful uterine contractions, which may seem to indicate the onset of labour. However, despite the contractions, progressive dilatation of the cervix fails to occur – this condition is termed false labour.

In it, the triple descending gradient of uterine activity fails to become established. A reverse gradient of uterine activity is present, the lower part of the uterus contracting nearly as strongly as the upper part. Because of this, cervical dilatation fails to occur and the pain of the uterine contractions is often felt as low backache.

Clinically, the painful contractions occur more often at night, but their frequency and intensity do not increase as time passes. A woman who complains of this pattern of uterine activity needs an explanation and, if the pains are distressing, requires treatment with analgesics, and perhaps a hypnotic so that she can enjoy a good night’s sleep.

Often the pains of false labour recur on a number of days and, in some cases, the reverse gradient of activity changes and true labour starts.

Onset of true labour

True labour may start and progress rapidly, or the start may be slow, with contractions only occurring at long intervals – the so-called sluggish uterus, or, in a more modern idiom, prolongation of the quiet (latent) phase of labour.

If the woman is becoming distressed that labour is not progressing, a more effective pattern of uterine activity can be obtained by performing an amniotomy and by starting an intravenous infusion of oxytocin. This regimen should only be instituted if there is no cephalopelvic disproportion and if the cervix is partly or wholly effaced, 2 cm dilated and soft.

The onset of labour is difficult to time with any degree of accuracy, and may be heralded by the following signs:

The transition into labour is gradual, but labour may be said to have begun when the cervix is at least 2 cm dilated and contractions become painful and regular, with diminishing intervals between each one.

Because of the difficulty in establishing the time of onset of labour with any degree of accuracy, many obstetricians mark its onset from the time the woman is admitted to hospital. This has advantages if the graphic method of recording the progress of labour (the partogram) is adopted.

Duration of labour

The duration of labour is not easy to determine precisely as its onset is often indefinite and subjective (Box 8.4). In studies of informed women whose labour started spontaneously there was a wide variation in the duration of labour, as can be seen in Table 8.1.

Table 8.1 Duration (and range) of labour (in hours)

Labour is usually shorter when the patient knows something of the physiology of normal labour, is in good physical and mental health at the onset of labour, and has confidence in her attendants. Delivery within 16 hours may be expected in 90% of nulliparous women (para 0), and the same proportion of multiparous women (para 1+) will deliver within 12 hours.

Admission

On admission the woman’s antenatal records are obtained and scrutinized for any past medical or obstetric problems, to check the history of the current pregnancy, and to make sure that the appropriate laboratory tests have been made. A history of the present labour is obtained, the frequency and strength of the uterine contractions are noted, and information is obtained about a ‘show’ of blood or mucus and whether or not the membranes have broken.

A general examination is made by a midwife or a doctor, the blood pressure, pulse and temperature being recorded. The abdomen is palpated to determine the presentation of the fetus and the position of the presenting part in relation to the pelvic brim (see Fig. 6.17). A vaginal examination may be carried out, with aseptic precautions, to determine the effacement and dilatation of the cervix and the position and station of the presenting part. The station of the presenting part is the level of the lowest fetal bony part (head or breech) in relation to an imaginary line joining the mother’s ischial spines. It is measured in centimetres above or below the ischial spines (Fig. 8.3). If the amniotic sac (the membranes) has ruptured this is noted. Evidence does not support the common practice of performing a routine 20-minute cardiotocogram (CTG) on admission in low-risk women. The ‘admission CTG’ is associated with higher intervention rates, i.e. augmentation of labour, epidural analgesia and operative delivery, without a clear improvement in neonatal outcome. The woman is transferred from the admission room to a bed in a delivery room (if she has not already been admitted to it) and a partogram is started which shows the progress of labour at a glance.

Fig. 8.3 Station of the head.

First stage of labour

The first stage of labour begins, as mentioned earlier, at an imprecise time. For convenience, labour is estimated to start when the patient says that the pains are becoming regular, or on her admission to hospital when the signs of labour are evident. It ends with the full dilatation of the cervix.

At the beginning of the first stage of labour the fetal presenting part (usually it is the head, so this term will be used in the rest of this chapter instead of the presenting part) has descended into the true pelvis to some extent. In a normally shaped pelvis the position of the occiput is in the transverse diameter of the pelvis in 75% of cases, in the oblique in 14% of cases, in the direct anterior position in 3% of cases, and in a posterior diameter in 8% of cases (Fig. 8.4).

Fig. 8.4 The positions of the vertex at the onset of labour and their relative frequency; the shaded positions are associated with a more difficult labour and delivery. OP, occipitoposterior; OT, occipitotransverse; OA, occipitoanterior.

The first stage of labour can be divided into a latent (quiet) phase and an active phase. In the early part of the latent phase the uterine contractions are relatively painless, occur at intervals of 5–10 minutes, and do not usually distress the patient. As the latent phase progresses the contractions become stronger and more frequent, but dilatation of the cervix is relatively slow. Towards the end of the phase the membranes may rupture spontaneously.

The active phase starts when the cervix is 3–4 cm dilated. The cervix dilates more rapidly in the active phase and the process is considered to be normal if it dilates at a rate of 0.5–1.0 cm/h. Towards the end of the active phase, when the cervix is 9 cm dilated, many women complain of very painful contractions and may have a desire to push. As it is unwise to push at this stage, a vaginal examination should be carried out to establish whether the cervix is fully dilated.

The duration of the latent and active phases is shown in Figure 8.5. If they last for more than 12 hours in a nulliparous woman, or more than 9 hours in a multiparous woman, the cause should be investigated (see Ch. 21).

Fig. 8.5 The phases of labour.

During the active part of the first stage of labour, the fetal head descends more deeply into the maternal pelvis and flexes (Figs 8.6–8.8).

Fig. 8.6 Late pregnancy. The fetal head has engaged in the transverse diameter of the pelvic brim and some flexion of the head on the chest has occurred. The cervix is soft but is not yet effaced, and the amniotic membranes are intact.

Fig. 8.7 Early labour. There has been further flexion of the fetal head and it has moved more deeply into the true pelvis, causing pressure on the bladder and rectum. The cervix has become effaced but has not yet begun to dilate, and the membranes are intact.

Fig. 8.8 Late first stage of labour. The cervix is now 7 cm dilated and further flexion of the fetal head has occurred. The membranes are still intact.

Second stage of labour

The second stage of labour begins when the cervix is fully dilated, to complete the formation of the curved birth canal, and ends with the birth of the baby. The second stage of labour is the expulsive stage, during which the fetus is forced through the birth canal. The uterine contractions become more frequent, recurring at 2–5-minute intervals, and are stronger, lasting 60–90 seconds. The fetal head descends deeply into the pelvis and, on reaching the gutter-shaped pelvic floor, rotates anteriorly (internal rotation) so that the occiput lies behind the symphysis pubis (Fig. 8.9). Anterior rotation occurs in 98% of cases, although in 2% of cases the head rotates posteriorly, with the result that the occiput lies in front of the sacrum.

Fig. 8.9 Early second stage. The cervix is fully dilated and the head is beginning to rotate at the level of the ischial spines. Rotation is through 90 °, so that the occiput of the fetal head lies in the anterior segment of the pelvis and the sagittal suture in the anterior–posterior diameter of the pelvis. The membranes are intact and bulge in front of the head.

The uterine contractions are now supplemented by voluntary muscle contractions. Simultaneously with the uterine contraction the patient holds her breath, closes her glottis, braces her feet and, taking a breath, holds it, grunts and contracts her diaphragm and her abdominal muscles to force the fetus lower in her pelvis. The energy expended causes her pulse to rise, and she sweats. As the uterine contraction diminishes and ceases, she relaxes and often dozes.

As the fetal head is pushed deeper into the pelvis the patient may complain of intense pressure on her rectum or pains radiating down her legs, caused by pressure on the sacral nerve plexus or obturator nerve. Some 15 minutes later the anus begins to open, exposing its anterior wall, and the head can be seen inside the vagina. With each contraction the fetal head becomes a little more visible, retreating a little between contractions but advancing slightly all the time (Fig. 8.10).

Fig. 8.10 Late second stage. The head is broaching the vulval ring – ‘crowning’. The membranes have ruptured, and the perineum is stretched over the head.

The head now presses on the posterior wall of the lower vagina and the perineum becomes thinner and stretched, its skin tense and shining. The woman complains of a ‘bursting’ feeling and a desire to push even without a uterine contraction. Soon a large part of the head can be seen between the stretched labia, and the parietal bosses become visible. The further sequence of the birth is shown in Figures 8.11 and 8.12, and is now described. With an extra effort the baby’s head is born, extending at the neck so that the forehead, the nose, the mouth and the chin appear in sequence. Mucus streams from the baby’s mouth and nose. After a short pause, the head rotates into a transverse diameter (external rotation). This brings the shoulders into the anterior–posterior diameter of the lower pelvis. The shoulders are born next, the anterior shoulder stemming from behind the symphysis and the posterior shoulder rolling over the perineum, followed by the baby’s trunk and legs. The baby gasps once or twice and cries vigorously. The uterus contracts to a size found at 20 weeks’ gestation.

Fig. 8.11 Birth of the head. As the fetal head is pushed through the vulval ring it extends on the neck and the perineum is swept over the face. The direction of movement of the head is now upwards. The uterus has retracted to fit closely over the fetal body. The shoulders are still in the transverse diameter of the midpelvis.

Fig. 8.12 Birth of the head. A sequence showing the progressive distension of the perineum by the head, which extends on the neck as it is born. The perineum sweeps over the forehead, face and chin. Once the head is born it drops slightly and then restitution (external rotation) occurs.

Head

As the fetal head (for this is the usual presenting part) becomes visible between the labia, the woman should be prepared for the birth. With each contraction the patient pushes and the fetal head becomes more visible, retracting slightly between contractions. When the area of the visible head has increased to 5 cm, and the perineum is thin and distended, the vulva should be swabbed with chlorhexidine (1 : 1000). The medical attendant who will deliver the baby now scrubs up and puts on gloves and gown. With each contraction the fetal head is flexed by the index finger of one of the attendant’s hands; the perineum is ‘protected’ by a pad which covers the perineum and the distended anus and is held in the attendant’s other hand. In some cases the perineum tears in spite of the protection; in others a deliberate incision (an episiotomy) is made to avoid such tearing. This is discussed later.

The manoeuvres described permit the head to be born slowly, until the parietal bosses are visible (when the head is said to be ‘crowned’). The mother now ceases to push with the contractions unless asked to do so by the medical attendant. Instead, she is asked to pant during each painful contraction.

To be born the fetal head now has to extend, and this is aided by the attendant’s left hand keeping the head flexed and the right hand holding the perineal pad pushing the chin upwards. The forehead, nose, mouth and chin emerge and the head is born, the perineum being pressed back behind the chin. The baby’s eyes are swabbed with sterile water and its head is rotated (or rotates itself) through 90 °. The attendant now puts a finger inside the woman’s vagina to feel whether the umbilical cord is around the baby’s neck. If it is, a loop of the cord is brought down.

Shoulders

As the baby’s head rotates, mucus streams from its mouth and nose. With the next contraction, the rotated head is grasped gently between the attendant’s two hands, which are placed over the sides of the head, and the head is drawn posteriorly so that the anterior shoulder is released from behind the pubic bones (Fig. 8.13). Following the birth of the anterior shoulder, the baby is swept upwards in an arc to release the posterior shoulder, followed by the body and the legs (Fig. 8.14).

Fig. 8.13 Birth of the anterior shoulder. With the birth of the head the shoulders reach the pelvic floor and, directed by the levator ‘gutter’, rotate to lie in the anteroposterior diameter of the pelvic outlet. The head therefore rotates externally, or undergoes ‘restitution’ to its position at the onset of labour. The anterior shoulder (in this case the right one) is appearing from behind the symphysis. The birth of the shoulder is aided by downward and backward traction of the head by the accoucheur.

Fig. 8.14 The birth of the posterior shoulder. The accoucheur aids the birth by lifting the head gently upwards while maintaining traction. This prevents damage to the perineum.

The mother should now be able to see and touch her baby. The baby is then laid between the mother’s legs and, if necessary, its mouth and fauces are sucked clear using a suction apparatus or a soft tube and bulb. The baby is placed between the mother’s legs so that it is below the level of the placenta, and its circulation will receive an additional 60 mL of blood as it drains from the placenta. One-third of this amount is received in the first 30 seconds after the birth and the remainder in the next 2–3 minutes. In normal cases (where the baby is not hypoxic) the attendant should not clamp, divide and tie the umbilical cord for about 2–3 minutes.

Vitamin K

Most neonates develop vitamin K deficiency by the third day of life. This predisposes the baby to a bleeding diathesis (haemorrhagic disease of the newborn) caused by the depression of clotting factors II, VII, IX and X. The baby may bleed from the gastrointestinal tract, the umbilical cord, or from skin punctures. A late-onset variety of vitamin K deficiency may affect breastfed babies between 4 and 6 weeks after birth. It manifests as gastrointestinal bleeding or intracranial haemorrhage. To prevent these possible problems it is currently recommended that all newborn babies should be given phytomenadione (vitamin K₁), either 1.0 mg intramuscularly at birth or 1.0 mg orally at birth, at 3–4 days and at 6 weeks of age. The further care of the newborn infant is described in Chapter 9.

Management of the third stage of labour

There are two methods of managing the third stage of labour:

Active management

As the fetal head is being born an intramuscular injection of Syntocinon 10 IU is given. The combination of oxytocin and ergometrine – Syntometrine – although widely used, is associated with a small reduction in blood loss but carries increased side-effects of nausea, vomiting and hypertension so the preferred routine prophylactic drug is Syntocinon.

The delivery of the baby following the injection is conducted slowly over 60 seconds. The umbilical cord is divided and clamped 2 minutes after the birth. The slowness is because the oxytocic effect takes about 2 minutes to produce a strong uterine contraction. The attendant’s left hand is placed on the uterus to detect the contraction. When it occurs, the hand is placed suprapubically and pushes the uterus upwards while the right hand grasps the umbilical cord and pulls the placenta out of the vagina in a controlled manner (Fig. 8.17). The membranes are drawn out intact by twisting them into a rope and pulling them out with a sponge forceps or the hand. In 1–2% of cases the placenta is retained, but no blood loss occurs. After a 10-minute delay another attempt is made to pull the placenta out by controlled cord traction. If this fails, manual removal is necessary (see p. 184).

Fig. 8.17 Controlled cord traction.

The advantages of active management are that maternal blood loss is reduced by a mean of 80 mL, postpartum haemorrhage (a loss of more than 500 mL of blood) is reduced from 4% to 2% of all deliveries, there is a lower requirement for blood transfusions and the third stage of labour is shortened. There is no difference in retained placenta or the need for manual removal of the placenta. The disadvantages include increased nausea and vomiting and hypertension if ergometrine, rather than oxytocin, is used. Injectable prostaglandins and oral misoprostol have been shown to be less effective than oxytocin and ergometrine for the routine management of the third stage.

Inspection of the placenta and membranes

The placenta and membranes are held up by the umbilical cord and the fetal surface is examined, attention being paid to the blood vessels to see if any run to the edge of the membranes, indicating a possible succenturiate lobe. The membranes are examined to make sure that no part remains in the uterus. The maternal surface of the placenta is examined next, any clots being washed away, so that the cotyledons can be inspected. The maternal surface is held in both hands and fitted together to make sure that no cotyledon has been left in the uterus. If any cotyledon is missing, or if most of the membranes have been left in the uterus or vagina, a doctor should explore the vagina and the uterine cavity under sterile conditions after ensuring that the woman has adequate anaesthesia.

Retained placenta

A retained placenta is one which has remained in the uterus for more than 1 hour. As a retained placenta may be associated with haemorrhage, action should be taken to remove it. The causes of a retained placenta are:

Episiotomy

Episiotomy – a deliberate incision in the stretched perineum and vagina – was first suggested about 200 years ago, to prevent a ragged perineal tear occurring which might extend to become a third- or fourth-degree tear. The idea was that episiotomy would prevent the development of such tears and would also prevent the later development of vaginal prolapse, although the evidence for this is dubious. Routine episiotomy has major disadvantages: the woman continues to have perineal pain and discomfort for longer than one who has not had the procedure, and in addition sexual intercourse may be uncomfortable for up to 6 months afterwards.

If the episiotomy has extended to produce a third- or fourth-degree tear, unless the anal sphincter is correctly sutured the woman may develop anal or urinary incontinence.

If the accoucheur thinks that an episiotomy is required because the fetal head is overdistending the woman’s perineum, they should explain what they propose to the patient. If the woman agrees to the procedure, the perineum should be infiltrated with a local anaesthetic, unless the woman has already had an epidural anaesthetic. The episiotomy incision may be midline or mediolateral (Fig. 8.18). The midline incision has the advantage that no large blood vessels are encountered and it is easier to repair. Its disadvantage is that it may extend into the rectum. If a large episiotomy is needed, for example when a difficult midforceps delivery is anticipated, a mediolateral episiotomy is preferred.

Fig. 8.18 Types of episiotomy.

One method of repairing an episiotomy is shown in Figure 8.19. This repair is the least painful postoperatively, particularly when 2/0 polyglycolic suture material is used.

Fig. 8.19 (A) Suture of the vaginal wall. (B) The suture of the vaginal wall has been completed and the perineal muscles are being sutured. (C) The subcuticular suture of the perineal skin, starting posteriorly and finishing deep to the hymen. (D) The two strands of catgut are tied, and cut short. The knot disappears beneath the vaginal mucosa.

Another method is to use continuous suture to repair the vagina and interrupted sutures for the perineal muscles and skin; a continuous subcuticular skin closure is associated with less pain and dyspareunia 3 months postpartum. The standard repair of an episiotomy is shown in Figure 8.20.

Fig. 8.20 Standard method of repair of an episiotomy or perineal tear.

Perineal tears

Four degrees of perineal tear are recognized:

First-degree tears are easy to repair; one or two sutures are all that is needed. Second- and third-degree tears need more care and their repair is shown in Figure 8.20. Third- and fourth-degree tears are uncommon, occurring in less than 1% of births. They usually follow a forceps delivery in a primigravida, the birth of a baby weighing more than 4 kg, or the delivery of a fetus persistently maintaining an occipitoposterior position. Careful repair is essential, but even then half of the women have persisting anal incontinence (usually only of flatus) for about 6 months owing to poorly repaired sphincter damage, and 4% have faecal incontinence. Pelvic exercises may resolve the problem, but if these fail surgery may be needed. Repair of fourth-degree tears requires considerable skill, and it is essential to secure the apex of the tear otherwise a rectovaginal fistula may result. The anal sphincter retracts when torn and its exposed ends must be identified and rejoined by sutures (Fig. 8.21).

Fig. 8.21 Repair of a fourth degree tear.

Postoperative care

The degree of postoperative pain and oedema depends on the method of delivery (forceps deliveries are followed by more oedema) and the quality of suturing. Most women need analgesics for a few days. A woman who has had the traditional interrupted sutures experiences more pain, but most patients can walk and have showers. Perineal swabbing is not usually necessary unless there is marked perineal oedema.

Episiotomies and perineal tears are not without longer-term discomfort. Twelve weeks after giving birth, 5% of women still experience some degree of pain and 15% have perineal discomfort. Sexual intercourse may be painful or uncomfortable for up to 20 weeks.

Lacerations of the lower genital tract

After a difficult delivery the vagina and the clitoral area should be inspected for lacerations. Any large laceration should be sutured. Continued bleeding in spite of a firmly contracted uterus suggests an internal laceration. The vagina and cervix should be inspected with good illumination. If a lacerated cervix is found the tear is sutured, care being taken to include the apex of the tear (Fig. 8.22).

Fig. 8.22 Repair of a cervical tear.

Non-pharmacological methods

The non-pharmacological methods need to be taught during the pregnancy by a trained person, so that by the time labour begins the woman understands what she has to do. They include massage and touch, relaxation techniques, rhythmical movements, heat and cold (e.g. showers or baths), and transcutaneous electrical nerve stimulation (TENS). The effectiveness of these techniques is not clear, but some women find them very helpful in relieving pain. Water immersion during the first stage of labour reduces the use of analgesia but does not affect the duration of labour, the rate of operative delivery or neonatal outcome.

Later in the active phase, when the contractions become stronger, a woman may choose to continue with non-pharmacological methods but must be made aware that if they do not provide adequate pain relief she may obtain treatment by a pharmacological method. She must not be made to feel that she has failed if she seeks narcotics or epidural anaesthesia.

Pharmacological methods

Of the narcotics, intramuscular pethidine at a dose of 100–150 mg at intervals is chosen by many women (the opioid is effective in about 15 minutes and the effect lasts for 2–3 hours). There is some concern that if pethidine is given within 2 hours before birth the baby may have a delayed onset of breathing. If this occurs it is easily and effectively treated by injecting an opioid antagonist, for example naloxone, either into the umbilical vein or intramuscularly.

An alternative method of giving pethidine, which is available in some hospitals, is patient-controlled analgesia (PCA). Using PCA the woman controls the dose she is receiving (within limits). The method is attractive to some women, particularly after a caesarean section, but it is not widely used.

Nitrous oxide and oxygen

In most cases a 50 : 50 mixture of nitrous oxide and oxygen is given in an Entonox machine. The patient breathes the mixture during a contraction in the active phase of the first stage and during the second stage of labour. It can be used to supplement the pain relief provided by pethidine. To be effective it has to be used properly, and even if this is the case, rather less than 50% of women obtain satisfactory pain relief; 20% obtain some relief, and 30% find the method ineffective.

Epidural analgesia

Epidural anaesthesia has become increasingly popular in recent years and would be chosen by more women if the service were more readily available. In Britain, for example, the Social Services Committee has recommended strongly that Health Authorities should provide an anaesthetic service in all major obstetric units that is available within a few minutes of receiving a call. The Committee also recommends that only specifically trained doctors should give an epidural anaesthetic.

Epidural anaesthesia is the most effective way of relieving the pain of childbirth, and provides complete relief of contraction pain in 95% of labouring women. It also provides great flexibility in pain management. For example, should the delivery require forceps or vacuum extraction or be by caesarean section, epidural anaesthesia avoids possible adverse biochemical effects associated with a general anaesthetic, and can provide postoperative pain relief. The disadvantages of epidural anaesthesia are that a few women complain of dizziness or shivering, and that it may increase the duration of the second stage and lead to an increase in operative vaginal deliveries. Epidurals can cause a small rise in maternal temperature and urinary retention, requiring catheterization, is common.

Serious side-effects are uncommon. The most worrying are transient hypotension, which occurs in 20% of patients, and dural tap (in 1%), which is followed by severe headache in half of the women. If the latter occurs the injection of a small volume of the woman’s blood into the dural space (blood patch) will prevent further leakage of cerebrospinal fluid and allow resolution of the headache. There is no increase in the rate of long-term back pain.

Local analgesia

Local analgesia is a choice in the relief of pain during childbirth for women who have not had an epidural anaesthetic and who require a forceps or vacuum extraction delivery; for the repair of an episiotomy or a perineal tear; and in some cases for breech delivery. Two techniques are available. These are pudendal nerve block and perineal nerve infiltration. To understand the techniques, knowledge of the nerve supply of the vulva and lower vagina is needed.

Nerve supply of the vulva

The female vulva is innervated mainly by branches of the pudendal nerve. The pudendal nerve, derived from S2, S3 and S4, leaves the pelvis medial to the sciatic nerve through the greater sciatic foramen. It then crosses the external surface of the ischial spine and re-enters the pelvis through the lesser sciatic notch and, passing along the lateral wall of the ischiorectal fossa, divides into branches that supply most of the perineum (Fig. 8.23). Further sensory branches to the skin of the perineum are derived from the ilioinguinal nerve, the pudendal branch of the posterior femoral cutaneous nerve and the genital branch of the genitofemoral nerve (Fig. 8.24).

Fig. 8.23 The course of the pudendal nerve. The area in the circle that lies just medial to and below the tip of the ischial spine is the area into which the local anaesthetic is infiltrated.

Fig. 8.24 Innervation of the perineum. On one side the nerves are shown, on the other, ‘fanlike’ local anaesthesia.

Technique of pudendal nerve block

A 10 cm 20-gauge needle and, if available, a needle director are required. Two fingers are introduced into the vagina to palpate the ischial spine, the guide containing the needle being introduced in the groove between the index and middle finger to impinge on the spine. The guide is then directed to lie just medial to, and below, the ischial spine, and the needle is advanced 1 cm beyond the guide (if no guide is available the needle is introduced between the fingers to the same site) and pushed through the sacrospinous ligament (Fig. 8.25); 10 mL of 0.5% lidocaine (lignocaine) are injected behind each ischial spine, and a further 10 mL are used to make a perineal infiltration. Anaesthesia should be effective within 5 minutes and it should be tested. The lower vagina and perineum become insensitive to pain. The use of pudendal nerve block is not without problems. For example, the needle may be difficult to introduce accurately in a relatively mobile patient, particularly when the fetal head is deeply engaged.

Fig. 8.25 Transvaginal pudendal nerve block.