Induction of Labour (IOL)
- Artificial initiation of uterine contractions prior to spontaneous onset
- Differs from augmentation when contractions of established labour are strengthened
- Performed when continuing pregnancy would expose mother/fetus to risk greater than that of induction
Indications
- Post dated pregnancy – 12 days or more beyond EDD (beyond 42wk gestation there is increased risk of stillbirth, fetal compromise during labour and meconium aspiration). This is the most common indication
- Fetal growth restriction
- Multiple pregnancy
- Pre-eclampsia
- Other maternal disorders – hypertension, diabetes
- Intrauterine death
- Prolonged prelabour rupture of membranes
- Unexplained antepartum haemorrhage
The Bishop Score
- Quantifies the state of the cervix in terms of:
- Dilation
- Length
- The station of the presenting part with regard to the ishial spines
- Consistency
- Position
- Dilation
- Higher scores are associated with shorter induction periods that are likely to be more successful
Methods
- Women with an unfavourable cervix may need up to 3 doses of vaginal prostaglandin E2 (2mg) after which time her membranes can be ruptured (using an amnihook) and if necessary she can be administered Syntocinon (i.v.) if she is not progressing
- If her cervix is favourable prostaglandin may not be required, ARM may suffice with or without Syntocinon
- Natural induction – cervical sweeping involves passing a finger into the cervix and parting the membranes from the lower segment of the uterus. At 40 weeks this reduces the chance of induction and post dated pregnancy
Complications
- Monitor with CTG – increased risk of fetal compromise
- May fail and the resulting hyper stimulation of the uterus may result in fetal asphyxiation and the need for a caesarean section
- If there is previous uterine scarring may lead to uterine rupture
- Risk of cord prolapse if ARM is performed when the presenting part is still high
- Increased risk of PPH