Define and describe the indications, contraindications, methods and complications of induction of Labour.

Bishop score predicts the likelihood of successful induction.

Definition

Induction of labour is the artificial initiation of uterine contractions, after the period of viability, before their spontaneous onset, with the aim of achieving vaginal delivery. (Augmentation is the enhancement of contractions that have already begun.)

Induction of Labour - Method BY Bishop Score

Indications

Conditions in which continuing the pregnancy is more hazardous than delivery — post-term pregnancy, pre-eclampsia, intra-uterine growth restriction, premature rupture of membranes at term, diabetes, Rh isoimmunisation, intra-uterine fetal death, chorioamnionitis and certain medical disorders.

Contraindications

Cephalopelvic disproportion, malpresentation (transverse lie), placenta praevia and vasa praevia, a previous classical caesarean or major uterine surgery, cord prolapse, active genital herpes, and established fetal distress (which needs immediate delivery, usually caesarean).

Assessment — the Bishop Score

The favourability of the cervix is graded by the modified Bishop's pre-induction scoring system, scoring cervical dilatation, effacement, consistency, position and the station of the head. A score ≥ 6 is favourable (induction likely to succeed); a low score calls for cervical ripening first.

Pre-requisites Before Induction

Before inducing, confirm a valid indication, a cephalic presentation with the head engaging and no disproportion, a reassuring fetal heart, and an assessed (and if necessary ripened) cervix. Confirm the gestational age, obtain informed consent, and ensure facilities for continuous monitoring and for emergency caesarean section.

Methods

Cervical ripening (for an unfavourable cervix)

• Prostaglandins — PGE₂ (dinoprostone) gel/pessary or PGE₁ (misoprostol).
• Mechanical — transcervical Foley/balloon catheter or hygroscopic dilators (laminaria).
• Membrane sweeping (stripping) — digital separation of the membranes from the lower segment releases local prostaglandins and may initiate labour; useful as a simple outpatient measure near term.

Medical

• Oxytocin infusion — titrated, with continuous fetal-heart and contraction monitoring (most effective once the cervix is favourable and the membranes are ruptured).

Surgical

• Amniotomy (artificial rupture of membranes, arm) — releases prostaglandins and is usually combined with oxytocin.

Conduct of Induction and Failed Induction

During induction, monitor the fetal heart and uterine contractions continuously, watch for hyperstimulation (more than five contractions in 10 minutes or sustained contractions, with fetal-heart changes — stop oxytocin, give a tocolytic, reposition and oxygenate), and chart progress on a partogram. Failed induction — failure to achieve active labour despite an adequate attempt — is an indication for caesarean section; the chance of failure is higher with a low Bishop score.

Complications

Failed induction (ending in caesarean section), uterine hyperstimulation with fetal distress, uterine rupture (especially in a scarred uterus), cord prolapse (after arm with a high head), intra-uterine infection, iatrogenic prematurity and an increased risk of postpartum haemorrhage.

WHY the Bishop Score Decides the Method

Understanding why the Bishop score is assessed before every induction explains why some inductions succeed easily and others end in caesarean section. Induction attempts to start labour artificially; whether it will succeed depends on whether the cervix is 'ripe' — soft, effaced, dilated, anterior, with the head well applied. The Bishop score quantifies precisely this (dilatation, effacement, station, consistency, position). If the score is favourable (≥6), the cervix is already primed, and simple amniotomy with an oxytocin infusion will usually establish labour. If it is unfavourable (<6), driving the uterus with oxytocin against an unripe cervix produces painful, prolonged, ineffective labour, fetal distress and a failed induction ending in caesarean section. Such a cervix must first be ripened — with prostaglandins (PGE2 gel or misoprostol), which soften and efface the cervix by dissolving its collagen, or mechanically with a Foley catheter balloon. Understanding that the state of the cervix, not the strength of the contractions, determines the success of induction explains why the Bishop score is the first step and why ripening must precede oxytocin in an unfavourable cervix.

WHY Hyperstimulation and Rupture Are the Key Dangers

A crucial safety concept is why induced and augmented labour must be monitored so closely. Both oxytocin and prostaglandins can cause uterine hyperstimulation — contractions that are too frequent (more than five in ten minutes), too long, or with inadequate relaxation between them. This matters because the placenta is perfused only between contractions: during a contraction the intramural vessels are compressed and blood flow largely ceases. If the uterus does not relax properly, the fetus is progressively deprived of oxygen, producing fetal distress — which is why continuous fetal heart monitoring is mandatory during induction. In the extreme, or in a uterus already scarred by a previous caesarean, sustained hyperstimulation can cause uterine rupture — catastrophic for mother and fetus (hence prostaglandins are used with great caution, and misoprostol avoided, in a woman with a scar). Hyperstimulation is managed by stopping the oxytocin (or removing the prostaglandin), turning the woman into the left lateral position, giving oxygen and fluids, and considering a tocolytic. Recognising that the danger lies in losing the relaxation phase explains the entire safety framework of induction.

• Induction = artificially starting labour when continuing the pregnancy is more dangerous than delivering (post-dates, pre-eclampsia, PROM, IUGR, IUFD, diabetes).
• Assess the cervix with the BISHOP score: favourable (≥6) → arm + oxytocin; unfavourable (<6) → ripen first (PGE2/misoprostol or Foley balloon).
• Contraindications: placenta praevia, transverse lie, cephalopelvic disproportion, active herpes, classical caesarean scar, fetal distress.
• Complications: hyperstimulation with fetal distress, failed induction, uterine rupture (especially with a scar), cord prolapse after arm, PPH.
• Continuous fetal monitoring is mandatory; for hyperstimulation — stop oxytocin, left lateral position, oxygen, tocolytic.