7.3 Labour induction


Triggering labour artificially before it begins naturally.

Broadly speaking, induction is a two-step sequence: the first part involves cervical ripening (effacement, mid-position, early dilation), the second, induction of contractions that dilate the cervix.

7.3.1 Indications

Induction of labour is not an emergency procedure. It should be done only when there is a clear indication, in a CEmONC facility (refer if necessary) to allow rapid intervention in the event of complications (e.g., uterine rupture or foetal distress).

When referral to a CEmONC facility is not possible or there is limited (or no) foetal monitoring, indications are restricted to the following situations:
– Intrauterine foetal death (Chapter 4, Section 4.11);
− Maternal indication for termination of pregnancy and non-viable foetus;
− Severe pre-eclampsia and eclampsia (Chapter 4, Section 4.5 and Section 4.6);
− Premature rupture of membranes with risk of infection (Chapter 4, Section 4.9).

Notes:
– Prolonged pregnancy (over 41 weeks LMP) is traditionally considered an indication for inducing labour; this is not made in practice, however, due to the frequent uncertainty about the due date.
− Suspected foetal macrosomia at term is not an indication for induction.

7.3.2 Methods1

Administration of prostaglandins

misoprostol 200 micrograms tablet:
25 micrograms PO (dissolve one tablet in 200 ml of water and give 25 ml of this solution) every 2 hours until good contractions are obtained; do not exceed 150 micrograms total dose;
or
50 micrograms vaginally into the posterior fornix (a quarter tablet) every 6 hours until good contractions are obtained; do not exceed 150 micrograms total dose.

Note: dose of misoprostol is different in case of intrauterine foetal death (Chapter 4, Section 4.11).

or
dinoprostone gel: 1 mg vaginally into the posterior fornix. A second dose may be administered after 6 hours if the patient has not gone into labour.

Wait 6 hours2 after the last dose of prostaglandins before using oxytocin during labour.

Artificial rupture of membranes and administration of oxytocin

Artificial rupture of membranes (Chapter 5, Section 5.3) is performed while applying gentle pressure (if needed) on the head through the abdomen to prevent cord prolapse.

Administration of oxytocin alone

This is not as effective as the other methods, but may be used if:
– Prostaglandins are not available;
– Bishop score is ≥ 6 (Table 7.1);
– Artificial rupture of membranes is not feasible because the foetal head is too high.

Mechanical method using a Foley catheter balloon

Wear sterile gloves. With a speculum in place, insert a 16-18G Foley catheter into the cervical canal, guiding it with fingers or forceps. Inflate the balloon with sterile water in 10 ml increments until it is well inflated in the cervix (30 ml, on average) and apply continuous light pressure (catheter taped to the inner thigh) for 24 hours maximum.

Stripping the membranes

During the vaginal examination, if the cervix is open, insert one finger into the internal os and separate the membranes with a circular motion. This can help start labour, or at least cervical ripening, in the following hours or days.

7.3.3 Conditions

The choice of induction method depends on the initial degree of cervical ripening. The riper the cervix, the more effective and rapid the induction.

Assessment of the cervix is facilitated by a scoring system for cervical ripening: the Bishop score.

Table 7.1 - Bishop Score (the higher the score, the riper the cervix)

Criteria

0

1

2

3

Cervical dilation (at the internal os)

closed

1 finger

2 fingers

> 2 fingers

Cervical length

long

mid-length

short

effaced

Position of the foetal head relative to the ischial spines, in cm (foetal station)

–3

–2

–1 or 0

+1 or +2

Cervical consistency

firm

medium

soft


Cervical position

posterior

mid position




The cervix is considered ripe, that is, favourable to induction, if the score is 6 or greater. Labour is induced by artificially rupturing the membranes and administering oxytocin.

If the cervix is unfavourable or unripe (score below 6, with at most a long, firm, posterior cervix), ripen the cervix using a prostaglandin before triggering contractions with oxytocin or, if prostaglandins are not available, use a mechanical method and then oxytocin.

Special situations

– Scarred uterus:

  • Foetus alive and viable: prostaglandins are contra-indicated:
    • if the cervix is unfavourable: mechanical induction and oxytocin or caesarean section;
    • if the cervix is favourable: artificial rupture of membranes and oxytocin at half-dose.
  • Foetus alive but non-viable: as for intrauterine foetal death.

– Intrauterine foetal death: see Chapter 4, Section 4.11.