Induction of Labour: A Clinical Review
Definition
Induction of labour (IOL) is the artificial initiation of uterine contractions before their spontaneous onset to achieve a vaginal delivery (1). It is a crucial therapeutic intervention performed only when a clear medical indication exists and the evidence suggests that the benefits of expeditious delivery for the mother, the fetus, or both, demonstrably outweigh the potential risks of continuing the pregnancy (1, 7). It is vital to distinguish IOL from the augmentation of labour, which refers to stimulating spontaneous contractions that are considered inadequate to produce progressive cervical change.
Epidemiology
In Malaysia, IOL is a common and critical obstetric procedure, performed daily in hospitals nationwide. Its practice is set against a complex and concerning backdrop of a steadily rising national Caesarean Section (CS) rate, which increased from 15.7% in 2006 to over 25% by 2015, with trends suggesting a continued climb (1). In this environment, IOL acts as a double-edged sword. A poorly indicated, improperly managed, or failed induction is a significant contributor to emergency CS rates (4). Conversely, the strategic and evidence-based application of IOL is a key strategy in reducing the overall CS rate. This is particularly true in specific patient groups, such as low-risk, first-time mothers who, according to landmark trials, may have a lower chance of CS with elective induction at 39 weeks compared to expectant management (1). Mastering IOL is therefore not just about managing a single patient, but also about contributing to a major national public health goal.
Indications for IOL
IOL is indicated when continuing the pregnancy poses a greater risk than intervening. The primary indications, based on the Malaysian Ministry of Health (MOH) 2021 Guideline, are (1):
Prolonged (Post-Dated) Pregnancy: This remains the most common indication. IOL is offered at 41 completed weeks of gestation because of a clear, progressive increase in perinatal risk. The risk of stillbirth, while low in absolute terms, rises sharply after 41 weeks, and IOL has been proven to reduce perinatal deaths and the incidence of meconium aspiration syndrome (1).
Prelabour Rupture of Membranes (PROM):
At Term (>37 weeks): When the membranes rupture, the primary barrier to ascending infection is lost. IOL should be commenced within 24 hours to reduce the risk of chorioamnionitis and neonatal sepsis. If the mother is a known Group B Streptococcus (GBS) carrier, IOL should be expedited and intravenous antibiotics started, as the risk of vertical transmission to the neonate increases with the duration of rupture (1).
Late Preterm (34+0 to 36+6 weeks): In this period, the fetal lungs are more mature. The balance of risk shifts in favour of delivery. IOL is recommended over expectant management because it significantly decreases maternal infection rates and length of hospital stay without increasing adverse neonatal respiratory outcomes (1).
Hypertensive Disorders in Pregnancy (HDP):
For well-controlled HDP on medication, delivery is offered between 37 and 38 weeks to mitigate the risks of worsening hypertension or developing superimposed pre-eclampsia (1).
For pre-eclampsia without severe features, delivery is recommended at 37 weeks, as the risk of adverse events increases beyond this point (11).
⚠️ Red Flag: For pre-eclampsia with severe features (e.g., uncontrolled severe hypertension, eclampsia, HELLP syndrome, or evidence of end-organ damage), delivery is a definitive treatment. It is indicated at 34 weeks, or at the time of diagnosis if later, after maternal stabilisation with magnesium sulphate and antihypertensives (5).
Diabetes in Pregnancy (Pre-gestational and Gestational):
For women requiring insulin or oral medication, delivery is recommended between 37 weeks and 38 weeks + 6 days. Poorly controlled diabetes can lead to placental insufficiency, increasing the risk of late-gestation stillbirth. IOL also reduces the risk of fetal macrosomia and its associated complication, shoulder dystocia (1).
Fetal Growth Restriction (FGR/IUGR): The timing is highly individualised based on umbilical artery Doppler studies, which reflect placental health. For term FGR, the decision requires careful consideration. Severe preterm FGR with abnormal Dopplers (absent or reversed end-diastolic flow) indicates significant placental failure and may necessitate delivery as early as 32-34 weeks to prevent intrauterine death (1, 11).
Twin Pregnancy: For uncomplicated dichorionic (non-identical) twins, IOL is offered at 37-38 weeks. For monochorionic (identical) twins, who share a single placenta, it is considered earlier, at 36-37 weeks, due to a higher intrinsic risk of stillbirth from placental dysfunction (1).
Elective IOL at 39 Weeks (Low-Risk Nullipara): Based on the landmark ARRIVE trial, which showed a lower CS rate (18.6% vs 22.2%), this may be considered in select cases (e.g., advanced maternal age, IVF pregnancy) in Malaysia. The cautious adoption reflects pragmatic concerns about labour ward capacity and staffing. A widespread elective IOL policy could overwhelm resources, paradoxically leading to poorly managed inductions and worse outcomes if not implemented carefully (1).
Physiology
The goal of IOL is to artificially trigger and then sustain the complex physiological cascade of natural labour. This is a two-stage process:
Cervical Ripening: This is the initial and most crucial step for an "unripe" (firm, long, closed) cervix, which is a poor predictor for successful induction. The process involves inducing changes in the cervical extracellular matrix. Pharmacological agents like Dinoprostone (PGE2) directly act on cervical tissue, increasing water content and activating enzymes like collagenase and elastase. This breaks down the rigid collagen network, causing the cervix to soften, efface (thin out), and begin to dilate. Mechanical methods, like a Foley balloon catheter, apply direct, sustained pressure to the internal os, which not only physically stretches the cervix but also stimulates the local release of endogenous prostaglandins, achieving a similar effect (1, 10).
Myometrial Contraction: Once the cervix is "favourable" (soft, thin, and partially dilated), the focus shifts to the uterus. The primary goal is to generate effective, coordinated, and regular contractions. This is primarily achieved with an intravenous infusion of synthetic oxytocin. Oxytocin binds to specific receptors in the myometrium (uterine muscle). The sensitivity of these receptors naturally increases towards term. The binding of oxytocin initiates a cascade that leads to an influx of calcium ions into the muscle cells, triggering powerful and sustained contractions that result in progressive cervical dilatation and fetal descent through the birth canal (1).
Prerequisites for Safe IOL
Before any induction, a thorough assessment is mandatory to ensure patient safety. This is the "presentation" for a candidate for IOL.
Diagnostic Clues: The key determinant of success is the Modified Bishop Score. A score of >7 is favourable, suggesting a high chance of success with amniotomy and oxytocin. A score of <7 is unfavourable and indicates the need for cervical ripening to improve the chances of a successful vaginal delivery (1).
Essential Prerequisites:
Accurate Gestational Age: Confirmed via a first-trimester ultrasound. This is non-negotiable to avoid the significant morbidity and mortality associated with iatrogenic prematurity (1).
Informed Consent: This is a formal process, not a tick-box exercise. A comprehensive discussion led by a medical officer or senior clinician must cover the "what, why, how, and what if": the specific indication, the proposed methods, the potential risks (hyperstimulation, fetal distress, uterine rupture, failed induction leading to CS), and alternative management plans. This must be clearly documented (1).
Maternal and Fetal Assessment:
Confirm cephalic presentation via abdominal palpation. Inducing a breech or transverse lie is contraindicated.
Perform a vaginal examination to calculate the Modified Bishop Score.
⚠️ Red Flag: A baseline reactive Cardiotocography (CTG) is mandatory to confirm fetal well-being immediately prior to starting induction. Commencing an induction in the presence of pre-existing fetal compromise is dangerous (1).
Availability of Emergency Facilities: IOL must only be performed in a facility with 24-hour access to Caesarean section services and neonatal resuscitation, as complications can arise rapidly and require immediate intervention (1).
Complications
IOL is a significant medical intervention and carries inherent risks that must be communicated clearly to the patient during the consent process.
Uterine Hyperstimulation: This is the most common complication, defined as excessive uterine activity (tachysystole: >5 contractions in 10 minutes, averaged over 30 mins) which, if it leads to fetal heart rate abnormalities, is termed hyperstimulation. It can compromise placental blood flow, leading to fetal hypoxia and distress. It is a primary risk of both prostaglandins and oxytocin (1).
Fetal Distress: Diagnosed via an abnormal CTG (e.g., persistent decelerations, bradycardia, loss of variability), it is often a direct consequence of uterine hyperstimulation or placental insufficiency that is unmasked by the stress of induced contractions (1).
Uterine Rupture: A rare but potentially fatal obstetric emergency. The risk is substantially higher in women with a previous uterine scar (VBAC), especially when prostaglandins are used (risk of 14 per 1000) compared to mechanical methods (9 per 1000). Key warning signs include sudden, severe abdominal pain that persists between contractions, loss of station of the fetal head, and acute fetal bradycardia (1).
Failed Induction: Defined as the inability to achieve the active phase of labour (cervical dilatation from 4cm) despite a full cycle of induction. It is a major cause of emergency CS and is more common in women with a very unfavourable cervix, nulliparity, and obesity (1).
Postpartum Haemorrhage (PPH): Prolonged exposure to high doses of synthetic oxytocin can lead to the downregulation and desensitisation of myometrial oxytocin receptors. This results in uterine atony (failure of the uterus to contract effectively after delivery), a leading cause of major PPH (12).
Cascade of Intervention: IOL is associated with a higher likelihood of subsequent interventions. Induced labour is often perceived as more painful, leading to higher rates of epidural use. It is also linked to higher rates of instrumental delivery (forceps or ventouse) and emergency CS compared to spontaneous labour (10).
Prognosis
The outcome of IOL depends heavily on the initial cervical state as quantified by the Bishop score. With a favourable score (>7), the prognosis for a successful vaginal delivery is high. However, an unfavourable cervix (<7), particularly in a first-time mother (nullipara), significantly increases the risk of a failed induction, which may necessitate a Caesarean section (1, 10). Other factors that predict a lower chance of success include pre-pregnancy obesity, advanced maternal age, and an indication of post-term pregnancy. Conversely, the ARRIVE trial showed that for the specific group of low-risk nulliparous women, elective IOL at 39 weeks can actually improve the prognosis for vaginal delivery, lowering the CS rate from 22.2% to 18.6% (1).
Contraindications to IOL
These are clinical situations where attempting IOL and vaginal delivery would be dangerous and are therefore absolutely or relatively contraindicated.
Absolute Contraindications: These are essentially contraindications to any vaginal delivery.
[Placenta Praevia or Vasa Praevia]: Attempting IOL is absolutely contraindicated as cervical dilatation would cause catastrophic, life-threatening haemorrhage from the placenta or unprotected fetal vessels covering the cervix (1).
[Abnormal Fetal Lie or Presentation]: A transverse, oblique, or unstable lie, or a footling breech presentation, makes a safe vaginal delivery impossible and mandates a CS (1).
[Umbilical Cord Prolapse]: This is a time-critical obstetric emergency requiring immediate CS to prevent fetal asphyxia from cord compression (1).
[Previous Major Uterine Surgery]: A history of a classical (vertical) CS or a myomectomy that involved deep entry into the uterine cavity carries an unacceptably high risk of uterine rupture during labour (1).
Relative Contraindications (Requiring Senior Consultant Input):
[Previous Caesarean Section (VBAC)]: While not an absolute contraindication, IOL in a woman attempting a Vaginal Birth After Caesarean (VBAC) is a high-risk situation. It is associated with a significantly increased risk of uterine rupture. The decision requires consultant approval, and mechanical methods (Foley balloon) are strongly preferred over prostaglandins to minimise this risk (1).
[Grandmultiparity (≥5 previous births)]: These women have a higher baseline risk of uterine rupture due to a stretched and potentially weaker myometrium, a risk that is amplified by induction agents (1).
Investigations
Immediate & Bedside Tests
Modified Bishop Score: This is the essential bedside assessment to determine cervical favourability. It is crucial for deciding the method of induction (the action) as it is the single most important predictor of success and the likelihood of needing cervical ripening agents (the rationale) (1).
Cardiotocography (CTG): A baseline reactive CTG is mandatory to confirm fetal well-being before starting (the action), as IOL should not commence if there is pre-existing fetal compromise. A reactive trace typically shows a baseline of 110-160 bpm, moderate variability, at least two accelerations in 20 minutes, and no decelerations (the rationale) (1).
Diagnostic Workup
First-Line Investigations:
Ultrasound Scan: An ultrasound is vital to confirm cephalic presentation, localise the placenta to definitively rule out praevia, and estimate fetal weight (the action). This helps prevent catastrophic complications and allows for planning for potential issues like shoulder dystocia in cases of suspected macrosomia (the rationale) (5).
Gold Standard:
The "gold standard" for a successful induction is not a single test but the achievement of the active phase of labour (progressive cervical dilatation from 4cm with regular, effective contractions). This is confirmed by performing serial vaginal examinations (1).
Monitoring & Staging
Continuous CTG: This is performed throughout active induction with intravenous oxytocin to continuously monitor for signs of fetal distress (the action), as uterine hyperstimulation can rapidly and severely compromise fetal oxygenation (the rationale) (1).
Serial Vaginal Examinations: Performed approximately every 4 hours in the active phase to assess the progress of labour (the action). This ensures that cervical dilatation is occurring at an adequate rate (approx. 1cm/hr) and helps to identify labour dystocia early, allowing for timely intervention (the rationale).
Management
Management Principles
The management of IOL focuses on achieving a safe vaginal delivery by following a structured, evidence-based pathway: ripening the cervix when necessary, stimulating effective uterine contractions, and maintaining vigilant maternal and fetal monitoring to pre-empt and manage complications (1).
The First Hour of Induction
This phase focuses on the correct initiation of the chosen induction agent based on the Bishop Score.
For an Unfavourable Cervix (Bishop Score <7):
Cervical Ripening: Administer a vaginal Dinoprostone (Prostin®) 3mg tablet, placing it high in the posterior vaginal fornix as per the MOH protocol (the action). This is done to soften and efface the cervix, making it amenable to labour (the rationale). A second dose may be given after 6 hours if labour is not established, with a maximum of 2 doses (6mg total) per cycle (1).
For a Favourable Cervix (Bishop Score >7):
Amniotomy (ARM): Artificially rupture the membranes with a sterile instrument, ensuring the fetal head is well-applied to the cervix to minimise the risk of cord prolapse (the action). This releases a gush of local prostaglandins and allows the fetal head to apply direct pressure to the cervix (the rationale).
Circulation (IV Access): Secure IV access and commence an intravenous oxytocin infusion according to the MOH high-dose regimen, starting at 2 mU/min (the action), to generate effective, regular uterine contractions and establish the active phase of labour (the rationale) (1).
Definitive Therapy
First-Line Treatment:
Unfavourable Cervix: Dinoprostone (PGE2) is the standard agent in Malaysia. High-yield point: Be aware that while the MOH guideline specifies a maximum of 6mg, a national survey showed many hospitals use higher doses out of clinical habit rather than evidence. Adhere to the official 6mg guideline and escalate to a senior if progress is inadequate to ensure safe, standardised care (1, 13).
Favourable Cervix: Amniotomy followed by an oxytocin infusion is the standard of care to efficiently establish and progress labour (1).
Second-Line/Escalation:
Failed Induction: If the active phase of labour is not achieved after one full cycle of induction, this constitutes a failed induction. The management plan must be made by a specialist and may involve a period of rest followed by another IOL attempt, or proceeding to a Caesarean section (1).
⚠️ Red Flag: Uterine Hyperstimulation with Fetal Distress:
STOP the offending agent: Immediately discontinue the intravenous oxytocin infusion or manually remove the vaginal prostaglandin tablet/pessary. This is the most critical first step.
Administer acute tocolysis with Terbutaline 250mcg IV/SC to rapidly relax the uterus and restore placental blood flow.
Initiate intrauterine resuscitation (position the woman in the left lateral position, administer high-flow oxygen via a face mask, and give an IV fluid bolus).
If the fetal heart rate pattern does not recover promptly, prepare for an urgent emergency CS (1).
Supportive & Symptomatic Care
Pain Relief: Induced labour is often more painful and intense than spontaneous labour. Proactively discuss and provide adequate analgesia. Options range from simple methods like Entonox and parenteral opioids (Pethidine) to epidural analgesia, which provides the most effective pain relief and should be offered (14).
Hydration and Nutrition: Ensure adequate hydration with IV fluids if necessary, and allow light meals in the early latent phase of induction to provide energy for the work of labour.
Psychological Support: Continuous communication, providing regular updates, explaining procedures, and involving the woman in decision-making are fundamental aspects of high-quality care that can reduce anxiety and improve the overall birth experience.
Key Nursing & Monitoring Instructions
Strict, continuous monitoring of uterine contractions (frequency, duration, strength) and fetal heart rate via CTG during active induction.
Monitor maternal vital signs (BP, pulse, temperature) 4-hourly, or more frequently if there are concerns.
Perform and document vaginal examinations every 4 hours in the active phase to assess labour progress.
Inform medical staff immediately if uterine hyperstimulation is detected, if there are any non-reassuring features on the CTG, or if the mother complains of severe, unremitting pain.
Long-Term Plan & Patient Education
Explain clearly from the outset that IOL can be a lengthy process, sometimes taking more than 24-48 hours, to manage expectations.
Educate the patient and her partner on the signs of active labour and the different types of pain relief available to them.
Discuss the possibility of failure and the potential need for an instrumental delivery or a Caesarean section as part of the initial consent process.
Provide continuous psychological support and reassurance, acknowledging the physical and emotional challenges of an induced labour.
When to Escalate
Call Your Senior (MO/Specialist) if:
The diagnosis of a failed induction is suspected after a full cycle of induction.
Uterine hyperstimulation or a non-reassuring CTG develops and does not resolve promptly with initial conservative measures.
The patient has a previous CS scar and is experiencing significant or persistent pain between contractions, as this could be the first sign of impending uterine rupture.
A decision for a third dose of Dinoprostone (>6mg total) is being considered, as this is outside the standard MOH guideline.
There is inadequate progress in the active phase of labour (e.g., <2cm dilatation in 4 hours).
Referral Criteria
Referral to the anaesthetist for consideration of epidural analgesia should be made early if requested by the patient.
An emergency "Code Red" or equivalent hospital-wide emergency call should be activated for suspected uterine rupture or cord prolapse, mobilising the entire senior obstetric, anaesthetic, and neonatal team for an immediate, life-saving Caesarean section.
References
Ministry of Health Malaysia. (2021). Guidelines on Induction of Labour. Putrajaya: MOH. https://www2.moh.gov.my/moh/resources/Penerbitan/Perkhidmatan%20OnG%20&%20Ped/O%20&%20G/4.Guidelines_On_Induction_Of_Labour_2021.pdf
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Selo-Ojeme, D. (2023). Induction of Labour. TeachMeObGyn. Retrieved July 15, 2025, from https://teachmeobgyn.com/labour/delivery/induction-of-labour/
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