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Chapter 14 Abnormal labour

David T Y. Liu, Mentor: Martin Whittle

CHAPTER CONTANTS

Abnormal uterine activity 109
False labour (spurious labour) 109
Management 109
Precipitate labour and delivery 110
Management 110
Sudden cessation of labour 110
Management 110
Prolonged labour 110
Abnormal contractions (powers) 110
Infrequent weak contractions (hypotonic uterine activity) 110
Frequent strong contractions (hypertonic contractions) 110
Incoordinate uterine activity 111
Passenger 112
Abnormal descent (passage) 112
Management 113
Deficient/delayed cervical dilatation (passage) 114
Consequences of prolonged labour 114
Fetus 114
Mother 114
General management 114
Trial of labour 114
Contraindications 114
Requirements 115
Failed trial of labour 115
Trial of scar or vaginal delivery 115
Contraindications 115
Requirements 115

Spontaneous onset of labour followed by efficient uterine activity and delivery around a time of 8 hours for multiparous and 12–14 hours for primiparous women is accepted as normal. Labour complicated by problems of uterine contractility or integrity (powers), adequacy of the pelvis (passage) and fetal complications (passenger) is considered abnormal.

ABNORMAL UTERINE ACTIVITY

False labour (spurious labour)

Braxton Hicks or practice contractions may be exceptionally uncomfortable or of longer duration, thus giving the impression that labour has started. Repeated episodes of false labour or spurious labour on the other hand can signify fetal compromise and the need for early delivery to avoid fetal death.

Management

• Assess the woman to establish whether or not she is in labour. Observe contraction strength and frequency; check cervix on admission and review 1–2 hours later. If the cervix is <4 cm and there is no dilatation over the observation period, she is either in the latent phase of labour or not in labour. Assess fetal wellbeing using a 20 minute cardiotocograph (CTG) (this is not a requirement of the National Institute of Health and Clinical Excellence). If deemed not in active labour and fetus is satisfactory, she may go to the ward to await events. If appropriate some women may even go home.
• The presence of risk factors, i.e. abnormalities in the pregnancy or a non-reassuring CTG, indicate the need for close surveillance with consideration to augment or induce labour.
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• Women should be fully informed, contribute to plans for their care and be aware of the reasons for the steps taken.

Precipitate labour and delivery

Labour resulting in delivery less than 2 hours after onset of uterine contractions is accepted as rapid or precipitate. Dangers include delivery in an unsuitable or non-sterile environment with risk of fetal and maternal trauma. Precipitate labour and delivery are possible in the following conditions:

• When there is little resistance to delivery. With an effaced cervix 3 cm or more dilated and the presenting part engaged and well applied, little harm is likely if labour is properly conducted in an appropriate environment. Women with a history of precipitate labours should be admitted around 38 weeks for induction of labour to control the situation.
• Rapid labour may follow sensitivity to or excessive use of oxytocics. The fetus is pushed rapidly through the birth canal by strong frequent uterine contractions. Fetal hypoxia and trauma together with soft tissue damage of the birth canal are likely. This should not happen in well-conducted labours.
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Management

• Anticipate the situation from the obstetric history. Women must be carefully selected for oxytocin stimulation. This is particularly important in grand multipara or in women with a history of short labours.
• Anticipate the condition if pelvic findings suggest the likelihood of rapid labour.
• The maternal and fetal conditions must be closely monitored. A midwife must be in attendance to supervise labour.
• Myometrial sensitivity to oxytocin (Syntocinon) is enhanced after prostaglandin usage.
• Following delivery, examine the soft tissue of the birth canal for possible damage.

Sudden cessation of labour

When labour stops suddenly suspect uterine rupture. Uterine rupture is usually, but not always, preceded by evidence of fetal distress and continuous lower abdominal pain.

Management

• Confirm the diagnosis.
• Assess maternal condition, treat if shocked.
• The globular outline of the uterus is lost, fetal parts may be readily palpable, the fetal heart sounds may be absent, lie may not be longitudinal.
• Cross-match blood, summon an experienced anaesthetist and senior obstetrician.
• Perform emergency laparotomy.
• If repair of the uterus is not possible proceed to hysterectomy. There is a place for subtotal hysterectomy in this situation.

Box 14.1 gives more information on uterine rupture.

Box 14.1 Uterine rupture

Classification

Rupture may be incomplete (intact peritoneum) or complete (uterine cavity communicates directly with peritoneum cavity). This complication occurs in between 1 in 140 and 1 in 300 labours with a uterine scar.

Associations

• Previous uterine damage or surgery, e.g. myomectomy that encroached into the uterine cavity, hysterotomy and perforations.
• Caesarean sections, particularly classic sections (may rupture before onset of labour). Multiple sections or sections with inadvertent extension or need for an inverted T incision (Chapter 17). History of infection may mean poor healing and a weaker scar.
• Obstructed labour.
• Oxytocic usage. The very unfavourable cervix, previous lower segment caesarean section and oxytocic augmentation in multiparous women require careful assessment and close observation.
• Prostaglandin pessaries should be used with caution when priming a cervix in the presence of a previous caesarean scar.
• Instrumental delivery, e.g. rotation forceps.
• Intrauterine manipulations, e.g. internal podalic version for assisted breech delivery. This complication contributes to maternal and high perinatal mortality. Prevention by attention to the above is important.

Diagnosis

See Chapter 17.

Subsequent care

• Provide an opportunity for counselling to explain reasons for this traumatic incident.
• Elective caesarean section and close antenatal surveillance is mandatory if further pregnancies are allowed when the uterus is salvaged.

PROLONGED LABOUR

Labour is prolonged if it lasts more than 24 hours. This concept is dangerous if it suggests the mistaken connotation that labour can continue for 24 hours before delay is diagnosed. Labour should be considered prolonged once it lags behind the normal partogram by 2–3 hours. This definition draws attention earlier to development of abnormality. Labour is prolonged because of:

• abnormal contractions (powers)
• abnormal descent of the presenting part of the fetus (passenger)
• deficient/delayed cervical dilatation (passage).

Abnormal contractions (powers)

Infrequent weak contractions (hypotonic uterine activity)

Most likely reason is misdiagnosis of labour. It has been said that the overstretched uterus does not labour well but evidence for this is thin.

Management

• Assess the woman’s status, support her morale and correct ketoacidosis.
• If there are no contraindications (exclude disproportion and malpresentation), augment labour by amniotomy with or without intravenous oxytocics.
• Maintain close surveillance.

Frequent strong contractions (hypertonic contractions)

These can follow the inappropriate use of oxytocics. Prolonged labour associated with strong contractions is seen principally in multiparous mothers with disproportion. The practised uterus mounts an increased effort to overcome the obstruction. The resultant frequent strong contractions and increased uterine tone result in both maternal and fetal distress. If allowed to continue tetanic uterine activity can occur. A retraction ring denoting the junction between the strong contracting upper uterine segment and the overstretched lower segment is observed as a late sign of imminent uterine rupture.

Management

• An abnormal fetal heart rate is often an early sign and should alert the attendant to the problem.
• Exclude overstimulation by oxytocics.
• Caesarean section is indicated for tetanic contractions and an overstretched lower segment. This should be considered even if the fetus is dead. Destructive operations for a dead fetus increase the risk of uterine rupture.
• If the situation is less acute, reassess presentation and position of the presenting part of the fetus. The mode of delivery will depend on the findings and include trial of forceps, rotation forceps or more usually caesarean section.
• Excessive uterine activity can sometimes be reduced using salbutamol (a tocolytic) by inhalation for immediate effect.

Incoordinate uterine activity

The pacemaker for myometrial activity is normally situated at the cornu of the uterus. When pacemaker activity develops at alternative sites and interrupts fundal dominance, irregular uterine contractions are produced and incoordinate uterine activity results. Incoordinate uterine activity produces poor uterine propulsive effort, increased uterine tone and intermittent painful strong uterine contractions (Figure 14.1). This is usually, but not exclusively a condition of primiparous women in whom an element of disproportion is present. This condition is more likely if the woman is frightened, distressed or anxious as in a first labour, particularly if she is over the age of 35 years.

image

Figure 14.1 Fundal dominance with (a) normal pacemaker activity and (b) ectopic pacemaker and incoordinated uterine activity. (c) Schematic illustration of ectopic pacemaker activity resulting in high amplitude and attenuated contraction waves of incoordinated activity.

Management

• Reassure, sedate if appropriate and prescribe analgesia. Epidural anaesthesia is particularly effective.
• More than 50% of these women may require assisted delivery. Group and save blood.
• Re-examine the woman to exclude absolute disproportion.
• If appropriate, rupture the membranes and apply direct fetal heart rate monitoring.
• Prescribe intravenous oxytocics if there is no contraindication to further labour. The use of oxytocics overrides pacemaker influence.
• Deliver by caesarean section if there is no progress after 2–4 hours of oxytocic therapy or if fetal distress develops.
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Passenger

Another cause for failure to progress is due to problems with the passenger (fetus/fetuses). There are four main factors:

1. malposition
2. fetus too big (macrosomia)
3. malpresentation
4. fetal abnormality

It is essential to exclude these factors when poor progress presents. Malposition can sometimes be corrected by the use of oxytocin but its injudicious use in the other situations may result in uterine rupture.

The occipitoposterior position (see Chapter 16) is a common cause of slow progress, particularly in primigravid mothers. Frequently this malposition is associated with backache and early membrane rupture. Potential for deflection, hence a larger fetal head diameter, together with need to rotate from a posterior position to a more optimum occipitoanterior position contributes to prolonged labour. Adequate uterine activity is necessary to ensure rotation. In an android pelvis, failure to achieve rotation to occipitoanterior results in arrest at occipitotransverse. This will need assisted rotational delivery if the fetal head is low down and disproportion is excluded. At mid-pelvic level the correct approach is for delivery by caesarean section.

Fetal abnormality includes conjoined twins or tumours, for example, cystic hygromas. In contemporary practice most of these are identified antenatally on ultrasound scanning. In twin labour, consider ‘locking’ when there is failure of descent despite ideal conditions. Caesarean section is usually required. The risk is highest when the first twin is breech.

Fetal abnormality also includes growth restriction. See Box 14.2 for procedures in cases of intrauterine growth restriction.

Box 14.2 Intrauterine growth restriction

• Confirm diagnosis from obstetric history and ultrasound measurements. Umbilical artery Doppler waveform and CTG trace can indicate impaired fetal–placental perfusion. Late-onset growth restriction may be associated with normal umbilical artery Doppler findings despite fetal compromise because of compensatory mechanisms.
• Determine if the fetus is anatomical and chromosomally normal. Fetal weight less than 500 g, presence of reverse end diastolic flow velocity in umbilical arteries, umbilical vein pulsations and CTG fetal heart rate decelerations forewarn of poor prognosis.
• Review situation with the woman and her partner and a neonatologist. Offer counselling where appropriate.
• Determine mode of delivery. Consider past obstetric history, past labour patterns and presenting cervical conditions. Before 34 weeks of pregnancy presence of severe fetal compromise and anticipated viability justifies elective caesarean section. Use intravenous oxytocin to induce labour (starting at 2–4 mU/min). This is similar to performing a contraction stress test. Appearance of decelerations necessitates delivery by caesarean section.
• Prostaglandin is not contraindicated when there are no Doppler or fetal heart rate signs of compromise.
• Perform caesarean section if induction of labour is not successful.
• Fetal heart rate monitoring and close surveillance is mandatory during labour if growth restriction is suspected.
• Use the lower midline vertical uterine incision for delivery for fetuses more than 750 gm and over 24 weeks’ gestation if lower uterine segment is poorly formed. Monitor fetal heart rate until just before skin incision.
• Consider general anaesthesia which is associated with less fetal acidaemia.
• In preterm fetuses with growth restriction, presence of pregnancy hypertension confers an advantage with reduced perinatal mortality. Perinatal mortality rises significantly after 40 weeks of pregnancy.
• A neonatologist must attend delivery as these babies have impaired metabolic adaptation, such as poor response to hypoglycaemic stress, and increased risk of necrotising enterocolitis and respiratory distress syndrome.

Abnormal descent (passage)

Any condition, which hinders descent, will prolong labour. Obstruction to descent is due to the following:

• Obstruction by a mass or tumour outside the uterus, for example, an ovarian cyst. Malpresentation and malposition is usual. Obstruction can be at any level such as the pelvic brim or upper half of the pelvis. This complication should be identified before the onset of labour. Delivery is by caesarean section. An experienced obstetrician is required to conduct or supervise any additional surgery.
• Masses such as fibroids arising from the uterus or cervix can interfere with descent of the fetus. Occasionally after a lengthy labour when little residual liquor is present, the uterus may be wrapped tightly around the fetus preventing descent. Caesarean section is required. A possible exception is where forceps delivery is prevented by tonic uterine contraction. When this occurs the uterus can be relaxed by amyl nitrate, salbutamol inhalation or halothane administration to allow vaginal delivery.
• The presence of an unsuspected degree of placenta praevia.
• Disproportion. This term describes the situation where the proportions or diameters of the pelvis are inadequate for the passage of the fetus. This terminology describes inadequacy of the pelvis to accommodate the fetal head, which has the largest diameter and is least compressible. Cephalo-pelvic disproportion is a relative concept. A larger than normal baby can produce disproportion in a pelvis which is of normal size. This concept is particularly relevant in multiparous labours. The present fetus may be larger in size than a fetus in a previous pregnancy so previous spontaneous delivery should not encourage complacency. Alternatively, a small or preterm baby may deliver with ease through a small or contracted pelvis. Disproportion may arise at any stage of labour or at any site along the pelvic canal. It is, however, usual to notice disproportion at the pelvic brim (inlet disproportion), at the level of the ischial spine (mid-pelvic disproportion at the plane of least diameters) and at the pelvic outlet (outlet disproportion). Labour is prolonged whenever disproportion is present.
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Management

• Perform vaginal examination to assess cervical status, station of the presenting part of the fetus, presence of caput and adequacy of the pelvis.
• Request erect lateral pelvimetry. Additional information concerning the shape of the sacrum and possible reasons for inlet disproportion may be obtained.
• Perform a caesarean section if absolute disproportion is diagnosed at the inlet, mid-pelvis or outlet. Absolute disproportion is present whenever any pelvic diameter is smaller than the biparietal diameter. For the average fetus a diameter of 9.5 cm is not adequate.
• Inlet disproportion is associated with a flat pelvis, spondylolisthesis, sacralisation of the fifth lumbar vertebra, pelvic deformity (rickets, osteomalacia) pelvic fracture or congenital defects (Naegele’s or Robert’s pelvis). If absolute disproportion is not evident (fetal head overlaps symphysis when an attempt is made to direct the head into the pelvis) and there is no contraindication to further labour, observe closely and review after two hours. Cord prolapse is a threat when the presenting part of the fetus is poorly applied. Delivery by caesarean section is usual.
• Mid-pelvic disproportion. Both the short, stocky, obese, hirsute woman and the tall athletic woman with boyish hips are susceptible. Malposition is common. If conditions are suitable for further labour, review after an interval of 2 hours. Deliver by caesarean section if there is no progress. If the cervix is fully dilated and there is no absolute disproportion, ventouse or forceps delivery by an experienced obstetrician may be attempted after correction of malposition.
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• Outlet disproportion. This presents classically as delay in the second stage. The cervix is fully dilated with the presenting part below the mid-plane. A trial of forceps is acceptable if absolute disproportion is excluded. Outlet disproportion must be excluded in a breech delivery.

Deficient/delayed cervical dilatation (passage)

Poor cervical dilatation reflects or contributes to the slow progress of labour.

• The cervix dilates less well if the presenting part of the fetus is poorly applied.
• Occurs in 5% of primigravidae. It can be associated with poor cervical response to pregnancy changes. Assisted delivery or caesarean section is likely.
• Strong labour with poor descent can produce an oedematous cervix and gives the impression that dilatation is regressing.
• Poor dilatation can reflect weak or incoordinated uterine activity.
• Poor dilatation can be associated with disproportion.
• A scarred or fibrotic cervix (following cerclage or cone biopsy) may not dilate despite the descent of the presenting part to the introitus. If there is failure to dilate beyond 5 cm or more, make 2 cm incisions in the cervix at the 5 and 7 o’clock regions and deliver by forceps (Figure 14.2). Cervical incisions are seldom performed because further extension during delivery with resultant haemorrhage and damage to the lower uterine segment can occur. Do not incise if the cervix is not thinned out – deliver by caesarean section.
image

Figure 14.2 Cervical incisions.

CONSEQUENCES OF PROLONGED LABOUR

Fetus

The consequences for the fetus include trauma, acidosis, hypoxic damage, infection and increased perinatal mortality and morbidity.

Mother

The consequences for the mother are reduced morale, exhaustion, dehydration, acidosis, infection and risk of uterine rupture. The need for surgical intervention increases mortality and morbidity. Ketoacidosis by itself can result in poor uterine activity and prolonged labour.

General management

• Anticipate likelihood of this complication before the onset of labour or at the initial assessment in the labour suite.
• Determine the cause of prolonged labour. Treat correctable causes.
• Determine if there is justification for further continuation of labour. Fetal or maternal compromise precludes further labour.
• Continuing labour must be closely monitored. Support maternal morale and include the woman and her partner in discussion of the likely outcome.
• Anticipate the possibility of a caesarean section (required for 80% mothers not responding to oxytocics).

TRIAL OF LABOUR

All labour can be considered a trial. The term ‘trial of labour’ is reserved for situations where possible complications of labour are anticipated. The trial assesses the adequacy of the pelvis and the ability of the fetus or mother to withstand labour.

Contraindications

• Absolute disproportion.
• Malpresentations such as face and brow.
• Breech presentation. The trunk is the smaller or more compressible part of the fetus. The dangerous situation where the body is delivered with entrapment of the larger fetal head can occur.
• Fetal compromise.
• Maternal complications such as severe preeclampsia or severe cardiac disease.
• A uterus already weakened, for example by previous surgery or caesarean section.
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Requirements

• Contraindications must be excluded.
• Presence of regular effective uterine contractions. The cautious augmentation of uterine activity by intravenous oxytocics may be required. The trial examines the outcome of contractions. It is not a trial to determine if contractions can be generated or maintained. If possible await spontaneous onset of labour.
• Rupture membranes once the fetal head engages and apply direct fetal heart rate monitoring.
• Close fetal and maternal surveillance is necessary.
• Assessment at 2–4 hour intervals should be made, preferably by the same person.
• There should be adequate analgesia.
• General anaesthesia and surgery may be required. Adjust oral intake and cross-match blood.
• Supportive nursing and full discussion of the situation with the woman must be maintained.

Failed trial of labour

The trial must be abandoned when:

• fetal distress develops
• maternal distress or complications arise
• there is no progress after 2–4 hours despite adequate uterine contractions.

If the anticipated problem is limited to the pelvic outlet and instrumental delivery is considered, the term trial of forceps or ventouse is used. Delivery is by caesarean section if the trial of labour or trial of instrumental delivery fails. Caesarean section is required for subsequent pregnancies if the fetal size is the same or larger.

TRIAL OF SCAR OR VAGINAL DELIVERY

This term is used when vaginal delivery is considered after a previous lower segment caesarean section, or on occasion, a hysterotomy where the midline incision is sited in the lower half of the uterus.

Contraindications

• Previous classic caesarean section.
• History of uterine damage or plastic reconstruction.
• Suspicion of disproportion.
• History of complications (e.g. infection) which might have affected healing after previous caesarean section or uterine surgery.
• Uterine tenderness when the uterine scar is palpated.

Requirements

Many obstetricians are loath to allow vaginal delivery after any caesarean section. Caesarean section is not without risk and when conditions are satisfactory vaginal delivery can be safer and provide the woman with an experience of normal childbirth. In less than ideal conditions attempts at vaginal delivery can result in uterine rupture. It is, therefore, important that:

• An experienced obstetrician assesses and decides on the mode of delivery.
• The pelvic diameters must be ideal.
• Labour is conducted in a properly equipped environment.
• Close surveillance of both fetal and maternal conditions are maintained.
• All attending staff are aware of the risks and signs of uterine rupture.
• Any expression of increased or continuous pain must be investigated, particularly when epidural analgesia is used. Scar tenderness necessitates suspension of the trial. Deliver by caesarean section.
• Impose a short second stage. Avoid excessive pushing by performing an episiotomy and the early use of instrumental delivery.
• An experienced obstetrician must supervise or conduct delivery.

The uterine scar may be weakened after each successive vaginal delivery. Repeated vaginal delivery after previous caesarean section must be conducted with extreme caution.

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