Key Facts

Normal labour is the process by which the fetus, placenta, and membranes are expelled through the birth canal. It involves regular, progressive uterine contractions leading to cervical effacement and dilatation, descent and delivery of the fetus, and expulsion of the placenta.

Epidemiology

• Approximately 700,000 births per year in the UK
• Spontaneous vaginal delivery rate: approximately 52-58%
• Mean duration of first labour: 8-12 hours (nulliparous), 4-6 hours (multiparous)
• Mean gestation at spontaneous onset: 40 weeks

Aetiology

• Onset triggered by complex interplay of maternal and fetal factors
• Fetal hypothalamic-pituitary-adrenal axis activation increases cortisol production
• Progesterone withdrawal (functional rather than absolute in humans)
• Increased prostaglandin production from the decidua and membranes
• Oxytocin receptor upregulation in the myometrium
• Inflammatory cascade activation

Pathophysiology

• Cervical ripening: collagen degradation, increased hyaluronic acid, water content
• Myometrial contractions become coordinated through gap junction formation
• Fundal dominance: contractions strongest at fundus, propagating downwards
• Cardinal movements of labour: engagement, descent, flexion, internal rotation, extension, restitution, external rotation, expulsion

First Stage of Labour

• Latent phase (0-4cm): irregular contractions, slow cervical change, may last many hours
• Active phase (4-10cm): regular painful contractions (3-4 in 10 minutes), progressive dilatation ≥0.5cm/hr
• Show (mucoid blood-stained discharge)
• Spontaneous rupture of membranes may occur

Second Stage of Labour

• Full dilatation to delivery of baby
• Passive second stage: full dilatation without involuntary expulsive efforts
• Active second stage: expulsive contractions with maternal pushing
• Urge to push, rectal pressure, perineal stretching

Third Stage of Labour

• Delivery of placenta and membranes
• Active management (recommended): oxytocin, controlled cord traction (reduces PPH risk)
• Physiological management: no oxytocin, awaiting signs of separation

Red Flags During Labour

• Meconium-stained liquor (particularly thick/particulate)
• Pathological CTG (requires immediate action)
• Prolonged second stage
• Fresh vaginal bleeding not consistent with show
• Maternal pyrexia (>38°C)
• Cord prolapse

Bedside

• Intermittent auscultation (IA) with Pinard stethoscope or Doppler: every 15 min in first stage, every 5 min in second stage
• CTG only if risk factors present (meconium, oxytocin use, epidural, previous CS, abnormal IA)
• Vaginal examination (4-hourly in active first stage)
• Partogram documentation
• Temperature, pulse, BP hourly
• Urinalysis (ketones, protein)

Bloods

• Not routinely required in normal labour
• Group and save available
• FBC if excessive bleeding or planned instrumental delivery

Imaging

• Ultrasound for fetal position if uncertain (occipitoposterior vs anterior)

Special Tests

• Fetal blood sampling (FBS) if pathological CTG: pH >7.25 normal, 7.20-7.25 borderline, <7.20 abnormal
• Lactate on FBS: >4.8 mmol/L abnormal

Non-pharmacological

• Birth environment: low-risk women offered choice of birth setting (home, midwifery unit, obstetric unit) per NICE CG190
• One-to-one midwifery care in established labour
• Mobilisation and upright positions encouraged
• Hydration and light diet in early labour
• Water immersion for pain relief (birthing pool)
• Breathing techniques, massage, TENS

Pharmacological

• Entonox (50% nitrous oxide / 50% oxygen): inhaled, self-administered
• Pethidine 100-150mg IM or diamorphine 5-7.5mg IM (opioid analgesia)
• Epidural analgesia: bupivacaine 0.1% with fentanyl 2 mcg/mL (effective but requires continuous CTG)
• Oxytocin augmentation if delay in first stage: start at 1-2 mU/min, titrate every 30 minutes (requires continuous CTG)
• Active management of third stage: oxytocin 10 IU IM with delivery of anterior shoulder or immediately after delivery

Surgical/Interventional

• Amniotomy (ARM) to augment labour if slow progress
• Episiotomy if clinically indicated (mediolateral in UK practice)
• Instrumental delivery (ventouse or forceps) for prolonged second stage or fetal compromise
• Emergency caesarean section if required

Referral Criteria

• Transfer from midwifery-led unit to obstetric unit if complications arise
• Senior obstetric review if partogram action line crossed
• Neonatal team if meconium, prematurity, or fetal compromise

• Spontaneous vaginal delivery rate in UK: approximately 52-58%
• Instrumental delivery rate: 12-15%
• Emergency caesarean rate: 15-16%
• Perineal tear rates: first degree 35%, second degree 30%, third/fourth degree (OASI) 2.9% overall
• PPH (>500 mL) occurs in approximately 5-10% of vaginal deliveries
• Maternal mortality from direct obstetric causes: approximately 4 per 100,000 maternities in the UK
• Neonatal outcomes excellent for term, uncomplicated vaginal delivery

Stages of Labour Summary

Birthplace Study Key Findings