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 infection (Chapter 4, Section 4.9).

Note: pregnancy over 41 weeks LMP is traditionally considered an indication for inducing labour. This indication is only applicable if the due date is known with certainty.

7.3.2 Methods1

Administration of prostaglandins

misoprostol PO: one 25 microgram tablet every 2 hours until good contractions are obtained; max. 8 doses or 200 micrograms per 24 hours
Wait 4 hours after the last dose of misoprostol before using oxytocin during labour.

Notes:
– If 25 microgram misoprostol tablets are not available, dissolve a 200 microgram tablet of misoprostol in 200 ml of water and administer 25 ml of this solution (25 ml = 25 micrograms).
– The oral route should be preferred2. If oral administration is not possible (vomiting, impaired consciousness), use vaginal route (25 micrograms of misoprostol into the posterior fornix every 6 hours until good contractions are obtained).  
– Note, in the event of intrauterine foetal death, dose of misoprostol may be different depending on gestational age
: see Chapter 4, Section 4.11.

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 in the following situation:
– Prostaglandins not available or contra-indicated;
– Bishop score ≥ 6 (Table 7.1);
– Artificial rupture of membranes not feasible because the foetal head is too high.
– Artificial rupture of membranes not recommended (HIV infected patient, breech presentation).

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 until it is well inflated in the cervix (30-50 ml) and apply continuous light pressure (catheter taped to the inner thigh) for 12 to 24 hours.

Notes:
– Limited evidence supports simultaneous use of a Foley catheter and oxytocin as a safe and effective method for induction of labour.3
– A Foley catheter should only be used simultaneously with a uterotonic, if delivery cannot be delayed (e.g. eclampsia). In this case, misoprostol should be preferred.4,5

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 cm)

2 fingers
(2-3 cm)

> 2 fingers
(≥ 4 cm)

Cervical length

long
(≥ 4 cm)

mid-length
(2-4 cm)

short
(1-2 cm)

effaced
(< 1 cm)

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 or contra-indicated, use a mechanical method and then oxytocin.

7.3.4 Special situations

– Scarred uterus:
• Foetus alive and viable: prostaglandins are contra-indicated:
 - the cervix is favourable: artificial rupture of membranes and oxytocin.
 - the cervix is unfavourable: mechanical induction and oxytocin or caesarean section.
For precautions for use of oxytocin see Section 7.4.4. It is contra-indicated in women with 2 or more uterine scars.
• Foetus alive but non-viable: as for intrauterine foetal death.

– Grand multiparity and/or overdistended uterus:
For precautions for use of oxytocin see 
Section 7.4.4
Whatever method used, induction of labour should be approached with caution as there is a risk of uterine rupture.

– Intrauterine foetal death: Chapter 4, Section 4.11.