Overview
Induction of labour (IOL) is the planned initiation of labour prior to its spontaneous onset. Uterine contractions are initiated artificially leading to progressive dilation and effecement of the cervix and delivery of the fetus. Generally, IOL is performed when the risk to fetus and/or mother due to continuation of pregnancy outweight those for bringing the pregnancy to an end. If IOL is contraindicated i.e. the chance of successful induction is minimal and the risk to the mother/fetus is high, then an elective caesarean delivery or spontaneous delivery is advised. Most of the contraindication for induction of labour are the same contraindications for vaginal delivery.
It can be done when the fetus is viable.
20-25% of deliveries occur following induction of labour.
Indications for induction of labour
| Category | Indications |
|---|---|
| Maternal indications | Maternal disease (diabetes, renal disease, chronic pulmonary disease), pre-eclampsia, chorioamnionitis, prelabour rupture of membranes (PROM) with positive GBS culture |
| Fetal indications | Post-term or post-date pregnancy (GBD 41+ weeks), intrauterine fetal death (IUFD), intrauterine growth restriction (IUGR), fetal malformations incompatible with life, rhesus iso-immunization |
Summary of maternal contraindications for induction of labour (bolded are absolute contraindications)
| Category | Indications |
|---|---|
| Maternal contraindications | Placenta previa, vasa previa, deteriorating maternal condition (due to antepartum hemorrhage, pre-eclampsia or cardiac disease), uterine scar |
| Fetal contraindications | Severe fetal compromise, malpresentation (transverse lie and footling breech), cord presentation, hydrocephalus, GBD < 34 weeks, , abnormal fetal heart rate |
- Maternal indications for induction of labour
- Maternal diabetes mellitus: IOL at 38 weeks (or earlier). To avoid dystocia due to macrosomia and fetal demise.
- Pre-eclampsia and maternal hypertension: Pre-eclampsia at term is a common indication for early delivery. If the pregnancy is very preterm (< 34 weeks) caesarean delivery is a better option.
- Chorioamnionitis
- Prelabour rupture of membranes (PROM): the longer the delay between rupture of membranes and delivery the greater the risk of chorioamnionitis, endometritis and morbidity to the mother and fetus. At term, IOL is indicated approximately 24 hours following membrane rupture. For preterm prelabour rupture of membranes (PPROM) IOL is indicated if there is evidence of maternal infection, fetal compromise or growth restriction (the risk of IOL should still be weighed)
- Antepartum haemorrhage caused by Placenta previa type I and II or accidental haemorrhage
- Renal disease
- Chronic pulmonary disease
- Intrahepatic cholestasis of pregnancy
- “Social reasons” to satisfy domestic and organizational needs of the woman
- Fetal indications for induction of labour
- Post-term pregnancy (GBD 41+ weeks): pregnancy extending beyond 42 weeks is associated with an increased risk of stillbirth, fetal compromise in labor, meconium aspiration and mechanical problems at delivery IOL is usually recommended between 41 and 42 weeks gestation (this should be accompanied by intensive serial fetal monitoring).
- Twin gestation continuing beyond 38 weeks: IOL at 38 weeks
- Fetal macrosomia (> 90th percentile): this is an indication for IOL even in the absence of maternal diabetes
- Intrauterine fetal death (IUFD)
- Intrauterine growth restriction (IUGR)
- Fetal malformations incompatible with life
- Rhesus iso-immunization
- Maternal contraindications for induction
- Vasa Previa
- Placenta previa
- Myomectomy with entry into the uterine cavity
- Previous classical hysterotomy (C-section scar)
- Inverted “T” uterine incision
- Active genital herpes outbreak
- Umbilical cord prolapse
- Cardiac disease in pregnancy
- GBD < 35 weeks
- Hypersensitivity to dinoprostone or its constituents
- Pelvic structural deformities
- Fetal contraindications for induction
- Placenta previa type 2B, 3 and 4
- Malpresentation (Transverse lie, Footling breech)
- Cord presentation
- Abnormal fetal heart rate
- Hydrocephalus
Bishop Score
Bishop score quantifies how far cervical dilatation and effacement has progressed prior to IOL. Induction tends to take longer if it is performed before cervical effacement and dilatation. A high bishop score is associated with an easier and shorter induction while a low bishop score is associated with a longer induction that is more likely to fail and result in caesarean delivery. For labour to be successfuly induced, the cervix should be favourable i.e. a high bishop score of > 7, particularly in nulliparas. Cervical ripening is usually indicated if the cervix is unfavourable (Bishop score is ≤ 6). Mechanical ripening should be done with caution if there is a low-lying placenta or placenta previa.
Bishop score
| Score | Consistency | Dilation (cm) | Effacement (%) | Fetal station | Position of cervix |
|---|---|---|---|---|---|
| 0 | Firm | 0 | 0-30 | -3 | Posterior |
| 1 | Medium | 1-2 | 40-50 | -2 | Mid-position |
| 2 | Soft | 3-4 | 60-70 | -1, 0 | Anterior |
| 3 | 5-6 | ≥ 80 | +1, +2 |
Methods of induction
Non-pharmacological methods of induction
| Method | Description |
|---|---|
| Membrane sweeping | A gloved finger is run around the inner rim of the membrane to separate the inferior membranes from the lower uterine segment. causing natural prostaglandins to be released. Used as an adjunct to other methods of induction, can be repeated and is only performed at term (often weekly from 40 weeks). Causes labour within 48 hours. |
| Artificial rupture of membranes (AROM) | An amniotomy hook or toothed forceps is used to rupture the membranes in a forewater (low) amniotomy. For a hindwater (high) amniotomy a Drew-smith catheter is introduced between the membranes and uterus above the presenting part. The cervix must be favourable. Check for cord prolapse after AROM. |
| Nipple stimulation | Induces labour within 72 hours. |
Pharmacological methods of cervical ripening and induction
| Method | Description | Dose |
|---|---|---|
| Oxytocin (Syntocinon) infusion | This is started immediatly after membranes have ruptured (either spontaneously or AROM) and is continued through the second, third and fourth stages of labour to prevent post-partum hemorrhage (PPH). Infusion causes contraction within 3 – 5 minutes. | IV 5 IU in 500 ml NS. Start at a low infusion rate e.g 10 drops per min, and increase every 30 minutes until 3-5 contractions are achieved in every 10 minutes or maximum 60 drops per minute |
| Dinoprostone (PGE2) | Inserted vaginally into the posterior fornix as a tablet or gel. | 0.5mg/3mL intracervical gel syringe q6-8h mx 3 doses in 24 hours or 10mg vaginal pessary in posterior fornix for 24 hours |
| Misoprostol (PGE1, Cytotec) | Can be given as a tablet per oral, or insert in the posterior fornix, or as a pessary. Has a high complication rate and is not recommended for women with a previous scar. Usually given to induce labour following intrauterine fetal death. | PO 25 mcg every 2 hours. Intravaginal 25mcg every 6 hours. |
| Mifepristone (antiprogesterone) | Usually given to induce labour following intrauterine fetal death |
Mechanical methods of cervical ripening
| Method | Description |
|---|---|
| Ostmotic dilator | A hydrophilic substances that absorb water and enlarges causing the cervix to dilate. Substances include seaweed (Laminaria) and synthetic substances (Lamicel and Dilapan) |
| Extraamniotic saline infusion | Infusion of saline between the uterine wall and amnion. This causes additional prostaglandin release |
| Transcervical foley | Extra-amniotic insertion of foley and inflation with sustained traction. This can be followed by amniotomy (AROM) and oxytocin infusion |
| Double balloon catheter | This is the same as transvervical foley, however a double ballon is used to cover both the internal and external cervical os |
Complications of induction of labour
- Maternal complications of induction
- Failed induction: Failed induction is when AROM is still impossible after the maximum number of doses of prostaglandin have been given or if the cervix remains uneffaced and < 3 cm dilated after AROM has been performed and oxytocin has been running for 6-8 hours with regular contractions. Give a rest period and try another method or consider caesarean delivery (especially in the case of pre-eclampsia or fetal growth restriciton)
- Uterine hyperstimulation: a side effect of synthetic prostaglandins and oxytocin. This can lead to fetal compromise. Contraction frequency of > 5 every 10 minutes should be treated by stopping oxytocin and starting a tocolytic (subcutaneous terbutaline)
- Uterine rupture: women with a previous scar are at a greater risk of uterine rupture. The risk is higher if prostaglandins are used
- Intrauterine infection (Chorioamnionitis, Endometritis)
- Amniotic fluid embolism (lanugo hair and fetal squames in post-mortem)
- Increased risk of PPH: long labour augmented with oxytocin predisposes to PPH secondary to uterine atony
- Abruptio placentae
- Precipitous labor
- Fetal complications of induction
- Fetal distress (Non-reassuring status)
- Fetal demise
- Neonatal sepsis
- Iatrogenic delivery of preterm infant
- Cord prolapse: if AROM is performed when th efetal head is high
- Increased risk of birth trauma
