Labor & Delivery

Labour looks like a mass of numbers, timings and eponymous manoeuvres. It reduces to a single interaction.

The organising tool is the three P's: the power, the passenger and the passage. Every abnormality of labour is a failure of one of them, and progress is the observable output of all three working together.

That framework tells you what to do when labour is not progressing, because the correct action depends entirely on which P has failed.

Inadequate power can be augmented with oxytocin. A malpositioned passenger may rotate, or may need help. An inadequate passage cannot be changed at all, which is why cephalopelvic disproportion is the one diagnosis that mandates caesarean section rather than augmentation.

Giving oxytocin to a woman whose problem is the passage is the classic and dangerous error, because it can rupture the uterus.

1. Normal Labour and Its Stages

Labour is regular painful uterine contractions producing progressive cervical effacement and dilatation. Contractions without cervical change are not labour.

The first stage runs from the onset of labour to full dilatation and has two phases. The latent phase is slow and variable, and the active phase is faster and more predictable.

The threshold between them has moved. The classical teaching placed the active phase at 4 centimetres, but current international guidance places it at 5 centimetres, because progress below that point is genuinely slow in many normal women.

The second stage runs from full dilatation to delivery of the baby, and it is divided into a passive phase before the urge to push and an active phase of maternal effort.

The third stage runs from delivery of the baby to delivery of the placenta. Active management with a uterotonic, controlled cord traction and uterine massage reduces postpartum haemorrhage and is standard.

Signs of placental separation are lengthening of the cord, a gush of blood, and the uterus becoming globular and rising in the abdomen, and traction before separation risks uterine inversion.

2. The Mechanism of Labour

The fetal head must negotiate a pelvis whose widest diameter changes orientation from inlet to outlet, and the cardinal movements are simply the consequence of that geometry.

The pelvic inlet is widest transversely, so the head engages with its sagittal suture in the transverse diameter. The outlet is widest anteroposteriorly, so the head must rotate before it can be delivered.

Flexion is the movement that matters most, because it substitutes the suboccipitobregmatic diameter of about 9.5 centimetres for the occipitofrontal diameter of about 11.5 centimetres.

That difference of 2 centimetres is what makes a deflexed head an obstructed labour and a flexed head a normal one, and it is why malposition is dangerous even when the pelvis is adequate.

3. Monitoring Progress

The partograph has been superseded. The World Health Organization introduced the Labour Care Guide in 2020 with the explicit intention of replacing it, and FIGO has endorsed that position.

Three changes matter and are examinable.

The active phase now begins at 5 centimetres rather than 4. The minimum acceptable rate of dilatation is 0.5 centimetres per hour rather than 1, because 1 centimetre per hour proved unrealistically fast for many women who went on to deliver normally. And the alert and action lines have been removed, with the second stage now included.

The reason for all three changes is the same: the old thresholds labelled normal women as abnormal, and each such label led to augmentation or caesarean section that was not needed.

That is a genuine harm rather than a technicality, because unnecessary intervention in a first labour commits a woman to a caesarean scar and all its consequences in every subsequent pregnancy.

Assessment records cervical dilatation, descent of the head, contraction frequency and duration, fetal heart rate, liquor colour, moulding and caput, and maternal observations.

Moulding and caput deserve emphasis. Increasing moulding with poor descent suggests disproportion, because the head is being compressed rather than descending.

4. Fetal Monitoring

Intermittent auscultation is appropriate for low-risk labour and does not increase adverse outcomes compared with continuous monitoring.

Continuous cardiotocography is used in high-risk labour. It has high sensitivity but low specificity for fetal compromise, which means it generates many false positives and therefore many unnecessary caesarean sections.

Interpretation examines four features: baseline rate, variability, accelerations and decelerations.

Reduced variability is the most concerning single feature, because variability reflects an intact autonomic nervous system responding to a well-oxygenated brain.

Decelerations are classified by their relationship to contractions. Early decelerations mirror the contraction and reflect head compression, and are benign. Variable decelerations vary in timing and shape and reflect cord compression. Late decelerations begin after the contraction peaks and recover after it ends, and they indicate uteroplacental insufficiency.

The mechanism explains the timing: reduced placental perfusion during a contraction produces hypoxaemia that takes time to develop and time to resolve, so the deceleration lags behind the contraction.

A sinusoidal pattern is rare and ominous, associated with severe fetal anaemia.

Fetal scalp blood sampling can clarify an abnormal trace by measuring pH directly, reducing unnecessary intervention where it is available.

5. When Labour Does Not Progress

The diagnosis is not simply slow labour. It is identifying which of the three P's has failed.

Inadequate power means contractions that are too infrequent, too short or too weak. It is the commonest cause and is treated with amniotomy and oxytocin augmentation.

The passenger may be malpositioned, malpresenting or too large. Occipitoposterior position is the commonest malposition, presenting with back pain, a longer labour and a deflexed head.

The passage may be inadequate through a contracted pelvis or, rarely, a soft tissue obstruction. This is the one P that cannot be modified.

Cephalopelvic disproportion is suggested by poor descent despite good contractions, increasing moulding and caput, and a head that remains high with full dilatation.

Obstructed labour is a distinct and dangerous entity, and it remains an important cause of maternal death and morbidity in India. Prolonged obstruction produces the Bandl ring, a pathological retraction ring visible as a groove across the abdomen, and it warns of impending uterine rupture.

Pressure necrosis of the bladder and vagina against the pubic bone produces obstetric fistula, which is the characteristic long-term consequence of neglected obstructed labour and is essentially a disease of delayed access to care.

6. Induction and Augmentation

Induction means starting labour; augmentation means strengthening labour that has already begun.

Indications for induction include post-term pregnancy, prelabour rupture of membranes, pre-eclampsia, diabetes, fetal growth restriction and intrauterine death.

The Bishop score predicts whether induction will succeed, scoring dilatation, effacement, consistency, position of the cervix and station of the head. A high score indicates a favourable cervix and a high chance of vaginal delivery.

An unfavourable cervix is ripened first, with prostaglandins or a mechanical method such as a balloon catheter, before oxytocin is used.

Oxytocin must be titrated, and the risk is uterine hyperstimulation, which reduces placental perfusion because the placenta is perfused between contractions rather than during them.

Contraindications to induction are the contraindications to vaginal delivery: placenta praevia, transverse lie, previous classical caesarean section, and active genital herpes.

Prostaglandins are used with particular caution in a woman with a previous caesarean scar, because they increase the risk of uterine rupture.

7. Preterm Labour and Ruptured Membranes

Preterm birth before 37 weeks is the leading cause of neonatal death worldwide, and India carries the largest absolute burden of any country.

The strongest predictor is a previous preterm birth, and a short cervix on transvaginal ultrasound in the second trimester identifies further risk. Vaginal progesterone reduces preterm birth in women with a short cervix, and cervical cerclage is used in selected women with a history of cervical insufficiency.

Tocolysis does not improve neonatal outcome by itself, and understanding why matters. Its purpose is to buy 48 hours, which is the time needed for antenatal corticosteroids to act and for transfer to a unit with neonatal facilities.

Nifedipine and atosiban are the usual agents. Tocolysis is not given where continuing the pregnancy is more dangerous than delivering, as in chorioamnionitis, abruption or a non-reassuring fetal state.

Prelabour rupture of membranes before term creates a direct conflict: continuing the pregnancy allows maturation but risks ascending infection, while delivering avoids infection but imposes prematurity.

Management is therefore expectant with antibiotics, corticosteroids and surveillance for infection, with delivery when infection appears or the gestation is late enough. Erythromycin is used and co-amoxiclav is avoided because it is associated with necrotising enterocolitis.

Chorioamnionitis presents with maternal fever, tachycardia, fetal tachycardia, uterine tenderness and offensive liquor, and it mandates delivery regardless of gestation.

8. Caesarean Section

Caesarean section rates have risen far above the level associated with improved outcomes, and both under-provision and over-provision cause harm.

The incision that matters is the one in the uterus, not the one in the skin. A lower segment transverse incision heals in the relatively inactive lower segment and carries a low rupture risk in a subsequent labour. A classical vertical incision cuts the contractile upper segment and carries a substantially higher rupture risk, which is why it contraindicates future labour.

Classical incisions are now used only in specific circumstances such as a very preterm poorly formed lower segment, transverse lie with the back down, or an anterior placenta praevia with dense adhesions.

Vaginal birth after caesarean is offered to most women with one previous lower segment incision, with success rates around three-quarters and a small absolute risk of scar rupture.

Scar rupture presents with scar tenderness, an abnormal fetal heart pattern, cessation of contractions, loss of station and maternal collapse, and the fetal heart abnormality is often the earliest sign. Induction, and particularly prostaglandins, raises the risk.

9. Malpresentation and Operative Delivery

Breech presentation occurs in around 3 to 4 per cent at term, and the types are frank, complete and footling.

External cephalic version is offered from around 37 weeks and reduces the caesarean rate. Where it fails or is declined, planned caesarean section is generally safer than vaginal breech delivery for the baby, though vaginal breech delivery remains a necessary skill.

Transverse lie at term cannot deliver vaginally and requires caesarean section, and a neglected transverse lie can result in a shoulder presentation with a prolapsed arm.

Instrumental delivery uses forceps or ventouse and requires strict prerequisites: full dilatation, ruptured membranes, an engaged head with position known, adequate analgesia, an empty bladder and no disproportion.

Ventouse carries a higher risk of cephalohaematoma and subgaleal haemorrhage; forceps carry a higher risk of maternal perineal trauma and facial nerve injury.

Shoulder dystocia is an obstetric emergency in which the anterior shoulder impacts behind the pubic symphysis after the head has delivered.

Management follows a defined sequence: call for help, McRoberts manoeuvre of hyperflexing the maternal hips, suprapubic pressure, then internal manoeuvres such as delivery of the posterior arm or Wood screw. Fundal pressure is contraindicated because it drives the shoulder further into the symphysis and risks uterine rupture.

The complications are brachial plexus injury, most often Erb palsy, humeral or clavicular fracture, and hypoxic injury from delay.

10. Analgesia and the Newborn

Epidural analgesia is the most effective form of labour analgesia. It lengthens the second stage and increases instrumental delivery rates, but current evidence does not show that it increases the caesarean section rate.

Complications include hypotension from sympathetic blockade, which is why a fluid preload and vigilance are needed, and post-dural puncture headache.

Pudendal block anaesthetises the perineum for instrumental delivery, and the pudendal nerve is blocked at the ischial spine, which is palpable transvaginally.

Delayed cord clamping, waiting at least a minute, improves neonatal iron stores and reduces anaemia in infancy, which is a substantial benefit in Indian populations where infant anaemia is highly prevalent.

Immediate skin-to-skin contact and early initiation of breastfeeding within the first hour are standard, supporting thermoregulation, bonding and lactation.

Perineal tears are graded from first, involving skin only, through second involving perineal muscle, third involving the anal sphincter complex, to fourth involving the anal mucosa. Third and fourth degree tears require careful repair by a trained operator, since inadequate repair causes faecal incontinence.

11. Worked Examples

Example 1. A primigravida at 6 centimetres has been dilating at 0.6 centimetres per hour for four hours. Contractions are strong, the fetal heart is normal and there is no moulding.

Under the older partograph, a rate below 1 centimetre per hour would have crossed the alert line and prompted intervention. Under the Labour Care Guide, the minimum acceptable rate is 0.5 centimetres per hour, so this labour is progressing normally.

No augmentation is required. Good contractions with no moulding also argue against both inadequate power and disproportion. Intervening here would risk hyperstimulation and an unnecessary caesarean section in a woman who is progressing.

Example 2. A multipara in prolonged labour has a transverse groove across the lower abdomen, the head remains high, and she is distressed with continuous pain.

This is a Bandl ring, a pathological retraction ring indicating obstructed labour with impending uterine rupture. The upper segment has retracted and thickened while the lower segment has thinned.

Oxytocin is absolutely contraindicated, because augmenting contractions against an obstruction will rupture the uterus. Immediate caesarean section is required after resuscitation.

Example 3. After delivery of the head, the shoulders fail to deliver and the head retracts against the perineum.

This is shoulder dystocia with the turtle sign. Help is called immediately and the clock is noted, because the risk of hypoxic injury rises with time.

McRoberts manoeuvre with suprapubic pressure resolves most cases by rotating the symphysis and freeing the anterior shoulder. Internal manoeuvres follow if needed. Fundal pressure must not be applied, since it worsens the impaction and risks uterine rupture.

Summary

• Labour is the interaction of power, passenger and passage.
• The failed P determines the treatment; only the passage cannot be modified.
• Oxytocin for a passage problem can rupture the uterus.
• Labour requires contractions producing cervical change, not contractions alone.
• The active phase now begins at 5 centimetres, not 4.
• The minimum acceptable dilatation rate is 0.5 centimetres per hour.
• The Labour Care Guide has replaced the partograph and removed alert and action lines.
• The old thresholds labelled normal women abnormal and caused unnecessary surgery.
• Signs of placental separation are cord lengthening, a gush of blood and a globular uterus.
• Traction before separation risks uterine inversion.
• The inlet is widest transversely, the outlet anteroposteriorly, hence internal rotation.
• Flexion substitutes a 9.5 centimetre diameter for an 11.5 centimetre one.
• Increasing moulding with poor descent suggests disproportion.
• Intermittent auscultation is adequate in low-risk labour.
• Cardiotocography is sensitive but not specific, so it causes unnecessary intervention.
• Reduced variability is the most concerning single feature.
• Early decelerations reflect head compression and are benign.
• Variable decelerations reflect cord compression.
• Late decelerations reflect uteroplacental insufficiency and lag behind the contraction.
• A sinusoidal pattern suggests severe fetal anaemia.
• Inadequate power is the commonest cause of poor progress and responds to oxytocin.
• Occipitoposterior is the commonest malposition and deflexes the head.
• A Bandl ring warns of impending uterine rupture.
• Obstetric fistula follows neglected obstructed labour.
• The Bishop score predicts the success of induction.
• Ripen an unfavourable cervix before using oxytocin.
• The placenta is perfused between contractions, so hyperstimulation causes hypoxia.
• Prostaglandins raise rupture risk in a woman with a previous caesarean scar.
• Tocolysis buys 48 hours for corticosteroids and transfer, nothing more.
• Erythromycin is used in preterm rupture; co-amoxiclav risks necrotising enterocolitis.
• Chorioamnionitis mandates delivery regardless of gestation.
• The uterine incision, not the skin incision, determines future rupture risk.
• A classical incision contraindicates future labour.
• Scar rupture often shows an abnormal fetal heart pattern first.
• Transverse lie at term requires caesarean section.
• External cephalic version from 37 weeks reduces the caesarean rate.
• Instrumental delivery requires full dilatation, known position and an engaged head.
• Ventouse risks subgaleal haemorrhage; forceps risk perineal and facial nerve injury.
• In shoulder dystocia use McRoberts and suprapubic pressure; never fundal pressure.
• Erb palsy is the classic brachial plexus injury.
• Epidural lengthens the second stage but does not raise the caesarean rate.
• The pudendal nerve is blocked at the ischial spine.
• Delayed cord clamping for at least a minute improves infant iron stores.
• Third degree tears involve the anal sphincter; fourth involve the anal mucosa.