Trial of Labour: Indications, Contraindications, Risks and More

Trial of labour is conducted in the presence of a minor or moderate degree of cephalopelvic disproportion in an attempt to achieve a vaginal delivery. The factors supporting the achievement of vaginal delivery in trial of labour are:

  • Effective uterine contractions ((the strength, frequency and duration of uterine contraction)
  • Moulding of the fetal head(the degree of moulding)
  • The “give” of the pelvis(i.e. stretch of the pelvic joints and ligaments)
  • The fortitude of the patient
  • The attitude of the midwife
trial of labour: indications and contraindications

What is trial of labour?

Trial of labour is defined as a test given to a woman with mild or moderate cephalopelvic disproportion (CPD) to see if she can deliver her baby vaginally  with least or no harm damage to herself and baby.

Factors that influence the prognosis in trial of labour

  • The membranes: In trial of labour, early rupture of the membrane prejudices the outlook for the mother and baby. Early rupture of the membranes may be complicated by prolapse of the cord, malpresentation, abnormal lie and intrauterine infection.
  • The fetal head: Moulding of the fetal head is of great importance. Poor moulding implies that the head will not able to pass through a borderline pelvis. If malpresentation occurs during the course of labour, the prognosis for the trial of labour is poor.
  • Maternal distress: The onset of maternal distress may put an end to trial of labour in order to save the maternal life via operative delivery.
  • Fetal distress:  Fetal distress from prolapse of the cord or any other cause may make it highly necessary to terminate a trial of labour.

Advantages of trial of labour

Trial of labour prevents unnecessary elective caesarean section in cases of minor degree of disproportion. This is particularly vital in developing countries where facilities for maternity service are poorly equipped and patients may not return for antenatal supervision after delivery by Caeserean section. These patients run the great risk of uterine rupture in subsequent pregnancies.

Another advantage is the avoidance of premature induction of labour (with its attendant risk) which is used to popularly practised in cases of suspected disproportion. Premature induction of labour refers to the delivery of a baby which may be too big for the maternal pelvis if delivered at term. It’s, however, not without risks. The patient may fail to go into labour and intrauterine infection may result in. if the patient goes into labour, a grossly premature baby may be delivered.

Wherever possible, vaginal delivery is to be preferred to an abdominal delivery. If, hence, trial of labour ensures a safe vaginal delivery, so much the better for all concerned.

Disadvantages of trial of labour

Trial of labour may fail and when it fails, the patient is naturally disappointed; she may have gone via a great deal of psychological trauma. Her failure to deliver per vias naturates (by the natural route) may affect her adversely.

She may have consider herself or her baby abnormal and she would think of many reasons why she is unable to do what others women seem to do without much mental or physical trauma.

Apart from psychological agony the patient and her attendants go through, if trial of labour has gone on too long, the risk of intrauterine infection with its consequences on both the mother and baby cannot be underestimated.

Conditions in which trial of scar is considered

These are:

  • Spontaneous labour
  • Only one caesarean section scar
  • Vertex presentation
  • No cephalopelvic disproportion
  • No doubt about the presentation.

Contraindications of trial of labour

Trial of labour should not be attempted in the following situations:

  • Elderly primigravida
  • Gross pelvic contraction or deformity
  • In the presence of pre-eclampsia, diabetes mellitus,  severe hypertension, cardiac disease and  other life-threatening conditions
  • In cases where previous trial of labour  has been unsuccessful
  • In the presence of malpresentation or malposition
  • In cases of previous Caeserean section

A trial of scar

When a woman has had a scar of Caeserean section or hysterotomy is given chance to deliver vaginally. This trial is given to see if the scar is strong enough to withstand the labour. Like trial of labour it has to be conducted in hospital.

A failure of trial scar is indicated by (a) pain and tenderness over the scar (b) slight vaginal bleeding and (c) slight raise in pulse. Vacuum is usually applied in 2nd stage if there is no sign of rupture.

Outcome of trial labour

When does a trial of labour fails? Trial of labour is said to be successful if the delivery of the baby is accomplished per vagina spontaneously or by forceps or vaccum extractor.  It is only when unfavourable conditions such as fetal or maternal distress or failure to advance after 6-8hours of good contraction make the delivery of the baby by Caeserean section necessary that trial of labour can be said to have failed.

The midwife’s duties during a trial of labour

Since there is a chance of obstruction during trial of labour, it should only be done in a hospital with facilities for emergency Caeserean section. The midwife should on no account undertake the conduct of trial of labour on her own responsibility without due arrangement for emergency.

The following are the roles of midwife during a trial of labour:

1. Duties to the patient:  It is advisable to explain the situation to the patient and forewarn her of possible operative interferences.  The patient should be carefully assessed on admission to determine the following:

  1. the establishment of labour;
  2. the presentation of the fetus, its position and relation to the pelvic brim;
  3. the flexion of the head;
  4. the fetal heart rate;
  5. the general condition of the mother.

The physical and the emotional states of the patient are very essential factors in trial of labour so the midwife should endeavour to improve the morale of the patient.  The patient is confined to bed to prevent early rupture of membranes, sedation is administered liberally to promote rest and avoid exhaustion and undue anxiety.  Stay   with   patient,   talk   to   her   have   the   labour   is progressing, and help her to be relaxed.

Adequate hydration of the patient is ensured by giving intravenous infusion of 5% glucose. Nothing per oral is allowed since operative interference may be at short notice. The danger of inhalation of vomitus during anaesthesia is hence prevented. However, she may be allowed sips of water.

The bladder and rectum should be emptied to facilitate descent of the fetal head. Encouragement of the patient and a friendly attitude on the part of the midwife will go a long way to boost the patient’s morale. Keep her as comfortable and as dry as possible. Strict asepsis is maintained to avoid infection.

trial of labour

2. Assessment of progress of labour:  the progress of labour is monitored by vigilant observations made by the midwife in the constant attendance of the patient. The observations are made on:

a. The uterine contractions: They type of uterine contractions (i.e. their frequency, strength and duration) are noted and recorded hourly and half-hourly towards the end of the labour.  The effects of these contractions on the patient and the fetus are also noted.

b. The descent of the presentation: The uterine contractions should facilitate the flexion and descent of the head into the pelvis. The descent of the head is determined abdominally hourly.

c. The maternal condition:  A half-hourly observation and record are made of the maternal pulse, blood pressure and respiration.  The temperature is recorded hourly and every specimen of urine the patient passes is tested to rule out albuminuria and acetonuria. Fluid chart is also kept and the midwife should inform the doctor at once if the patient can no longer endure the ordeal.

d. The fetal condition: The fetal heart sound is auscultated and recorded quarter-hourly on a graph sheet.  Signs of fetal distress should be watched out for and prompt action taken when noticed.

3. Conditions to report to the doctor: The doctor should be informed for the following conditions:

a. abnormal /unsatisfactory uterine actions:  The midwife should report hypertonic or incoordinate uterine actions.

b. abnormal presentation: That is change from vertex to brow or face presentation.

c. rupture of membranes before full dilation: The time of tis occurrence and number of hours the patient has been in labour should be reported by the midwife. This is done to so that the doctor may do a vaginal examination to rule out cord prolapse and to determine the progress of labour.  It is not advisable to for the patient to have many vaginal examinations as these increase risk of infections.

d. signs of maternal or fetal distress: This should be reported promptly.

e. failure of descent of the presenting part in the presence of good uterine contraction: That is , a high head after 6 to 8 hours of strong uterine actions.

When any of the three complications occurs, Caeserean section will be done to expedite delivery and save both life of mother and baby.