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Induction of Labour
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Induction of Labour

Topics / Obstetrics and Gynaecology / Pharmacology

Indications

Maternal
  1. Hypertension in Pregnancy, Pre-eclampsia
  2. PROM and PPROM
  3. Chorioamnionitis
  4. Maternal comorbidities, such as Diabetes Mellitus
Fetal
  1. Severe growth restriction
  2. Postdates pregnancy
  3. Intrauterine Fetal Demise

Contraindications

Absolute
  1. Any contraindication to vaginal delivery.
  2. Cephalopelvic disproportion
  3. Placenta praevia
  4. Vasa praevia
  5. Cord prolapse
  6. Abnormal lie (Transverse lie)
  7. Previous classical Caesarean section
Relative
  1. Breech presentation
  2. Grande multipara
  3. Previous c-section (low transverse c-sections)

Bishop Score

The Bishop score helps you assess the ripeness of the cervix. The Bishop score is assessed before induction and during the induction process. You should add up the score from the 5 components: Dilatation, effacement, station, consistency and position. A score of 7 or more usually indicates that induction will probably be successful. 

Modified Bishop Score
0 1 2 3
1.Dilatation <1cm 1-2cm 2-4cm >4cm
2.Effacement (length) >4cm 2-4cm 1-2cm <1cm
3.Station -3 -2 -1/0 Vertex Engaged
4.Consistency Firm Average Soft -
5.Position Posterior Mid-Anterior - -

Induction of Labour Step-Wise

  1. Confirm the indication for induction of labour (IOL).
  2. Confirm fetal maturity. If not done yet, ultrasound should be performed to rule out contraindications for an IOL. 
  3. Review and determine contraindications for IOL.
  4. Location:
    • Close monitoring prior to and during induction is required.
    • Staff should be knowledgeable in the management of uterine hypertonus, intrauterine resuscitation, and emergency c-sections.
    • Informed consent should be done as Misoprostol usage is not approved for IOL.
  5. Cervical assessment:
    • Modified Bishop score 9 or more:
      • Options: Prostaglandins, Oxytocin, Artificial Rupture of Membranes (Amniotomy).
      • Misoprostol (E1):
        • Misoprostol 200ug is diluted in 200ml of water, therefore 1ug/ml. 
        • Institutions have their own protocol for the usage of Misoprostol.
        • Misoprostol (E1), 20ug PO every 2 hours x3, then 40ug PO every 2 hours x2 then 60ug PO as a last dose0.
        • Can also be given as 25 – 50ug PV in nulliparous women with a Bishop score less than 4, then repeated as 25ug after 4 and 8 hours.
        • FIGO’s 2017 Misoprostol regimen’s states that Misoprostol can be used as 25ug PV 6 hourly or 25ug PO 2 hourly. 
        • NB: The next dose should be omitted if the patient develops contractions.
      • Oxytocin:
        • The use of oxytocin alone does not appear to be as effective in a patient with intact membranes. Hence, better to be used after the artificial rupture of membranes, especially if no contractions occur within 1 hour.
      • Amniotomy:
        • Should be reserved for HIV-negative patients. Amniotomy should be performed when the fetal head has been engaged, this reduces the risk of cord prolapse.
    • Modified Bishop scores less than 9:
      • Prostaglandins
      • Multiparous women are at risk of uterine rupture, thus mechanical induction should be performed with a sterile Foley catheter.
    • Modified Bishop scores less than 6:
      • Options: Prostaglandins
  6. Monitoring:
    • Monitor maternal and fetal conditions before and after the administration of each dose.
  7. Delivery:
    • If the first cycle for induction of labour fails, depending on the situation, some institutions provide the patient with a “rest” day and then another cycle for induction of labour. 
    • However, if induction of labour fails you will need to prepare the patient for a c-section. 
    • If fetal distress occurs, an emergency c-section should be performed. 

Other Methods of Induction

These methods promote the release of endogenous prostaglandins
  1. Membrane stripping: The finger is inserted through the cervix and is moved around between the membranes and the lower segment of the uterus.
  2. Foley’s Catheter: Using a sterile technique, a foley catheter is inserted into the endocervical canal and it is inflated with sterile saline (60ml), stretching the cervix and releasing prostaglandins.

Complications

– Uterine hyperstimulation (fetal distress, uterine rupture) – especially with prostaglandins. Should be managed by stopping the agent, tocolysis, and emergency c-section as required.
– Failure of induction 
– Cord prolapse – especially if the fetal head is high, the cord can be found between the fetal head and cervix, and on the rupture of the membranes the cord prolapses.
– The risk of Prematurity 
– Increased rate of assisted deliveries
– Mother to Child Transmission of HIV

Caution and Notes

  1. There should be at least a 6-hour gap between the last prostaglandin dose and the administration of oxytocin.
  2. In the 2008 NICE guidelines, it is advised that amniotomy +/- oxytocin should not be used as the primary method of induction of labour unless the use of prostaglandins is contraindicated (there is a high risk of uterine hyperstimulation)
  3. There are many drugs registered for the induction of labour in South Africa: Prostaglandin E (Prandin E2, Prepidil Gel, Prostin E2, Propess), Prostaglandin F (Prostin F2 Alpha) and Oxytocin.
  4. The NICE guidelines consider the IOL as failed if the patient is not in labour after one cycle. After the initial cycle fails, the situation should be re-assessed and you may either try again or deliver the patient using a c-section.
Published on January 7, 2023
Dr RW Becerra Estevez
Dr RW Becerra EstevezMBChB (WSU)

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