Induction of labour is the artificial initiation of uterine contractions leading to progressive dilation and effacement of the cervix and delivery of the fetus. It can be done when the fetus is viable. For labour to be induced, the cervix should be favourable (Bishop score > 7; particularly in Nullips). 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. The contraindications for induction of labour are the same contraindications for vaginal delivery.
25% of women have their labour induced.
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 |
- Maternal indications for induction of labour
- Maternal disease
- Diabetes mellitus (avoid dystocia d/t macrosomia and fetal demise)
- Renal disease
- Chronic pulmonary disease
- Obstetric complications
- Pre-eclampsia
- Chorioamnionitis
- Term rupture of membranes with positive GBS culture
- Antepartum haemorrhage caused by Placenta previa type I and II or accidental haemorrhage
- Maternal disease
- Fetal indications for induction of labour
- Post-term pregnancy (GBD 41+ weeks)
- IUFD
- 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
- Mechanical methods for cervical ripening
- Osmotic dilator: hydrophilic substances that absorb water and enlarge causing the cervix to dilate
- Seaweed (Laminaria)
- Synthetics (Lamicel and Dilapan)
- Extraamniotic saline infusion: infusion of saline between the uterine wall and amnion causes additional prostaglandin release.
- Transcervical Foley: extra-amniotic insertion of foley and inflation with sustained traction f/b → amniotomy → oxytocin
- Double balloon catheters: same as transcervical foley but double balloon covers both the internal and external cervical os.
- Osmotic dilator: hydrophilic substances that absorb water and enlarge causing the cervix to dilate
- Pharmacological methods for cervical ripening and induction
- Oxytocin (Syntocinon) Infusion causes contractions within 3-5 minutes. Commenced immediately after amniotomy. CT drip through 2nd, the third, and fourth stages of labour to prevent PPH.
- IV 5 IU in 500ml NS.
- Misoprostol (PGE1, Cytotec) Not recommended with previous C/S scar
- PO 200mcg q2h
- Intravaginal 25 mcg q6h
- Dinoprostone (PGE2)
- 0.5mg/3mL intracervical gel syringe q6-8h mx 3 doses in 24 hours or
- 10mg vaginal pessary in posterior fornix for 24 hours
- Oxytocin (Syntocinon) Infusion causes contractions within 3-5 minutes. Commenced immediately after amniotomy. CT drip through 2nd, the third, and fourth stages of labour to prevent PPH.
- Non-pharmacologic methods for cervical ripening and induction
- Membrane stripping: Perform VE, place your finger into the cervical os and perform a circular motion to separate inferior membranes from the lower uterine segment. Causes labour within 48 hours.
- Amniotomy (Artificial rupture of membranes, AROM) using an amniotomy hook/toothed forceps/Kocher’s forceps. Check for cord prolapse after AROM.
- Forewater (low) amniotomy: strip membranes → rupture forewater with amnihook
- Hindwater (high) amniotomy: Introduce Drew-Smythe catheter between membranes and uterus above the presenting part
- Nipple stimulation causes labor within 72 hours
- Maternal complications of induction
- Failed induction (try another method or consider C/S)
- Uterine hyperstimulation
- Uterine rupture
- Intrauterine infection (Chorioamnionitis, Endometritis)
- Amniotic fluid embolism (lanugo hair in post-mortem)
- Increased risk of PPH
- Abruptio placentae
- Precipitous labor
- Fetal complications of induction
- Fetal distress (Non-reassuring status)
- Fetal demise
- Neonatal sepsis
- Iatrogenic delivery of preterm infant
- Cord prolapse
- Increased risk of birth trauma