Table of Contents
Labour = expulsion of products of conception after 24 weeks gestation.
1st stage of labour (cervical dilation)
- Timing: 12-15 hours if primiparous (1cm/2 hours), 7.5 hours if multiparous (1cm/hour). It is usually divided into the latent phase (cervical dilation 0-3cm) and active phase (cervical dilation 3-10cm).
- Signs:
- ‘Show’ (passage of blood stained mucus)
- Regular painful contractions (3-4 in 10 minutes)
- Rupture of membranes
- Mechanism: fetal head descends into pelvis
- Complications: 3 Ps
- Passenger: cephalopelvic disproportion, fetal malpresentation (e.g. persistent occipito-posterior position)
- Passage: fibroids, cervical stenosis, narrow mid-pelvis
- Power: primary uterine inertia
- Interventions may include: C-section (e.g. for cephalopelvic disproportion), oxytocin (for contractions)
- Other points: induction of labour may be required for overdue babies, and it may be initiated by a membrane sweep, prostaglandin gel/pessary or artificial rupture of membranes
2nd stage of labour (expulsion of foetus)
- Timing: 45-120 minutes if primiparous, 15-45 minutes if multiparous
- Signs: first sign is desire to bear down
- Mechanism: most common starting position is left occiput anterior (see below)
- Flexed fetus descends: fetal head is very flexed on spine and descends downwards
- Internal rotation: whole fetus internally rotates (until facing towards maternal back; head at level of ischial spines)
- Extension of head: head extends around pubic symphysis until delivery
- Restitution (external rotation): after head delivered, fetus rotates back to its original position (i.e. with shoulders antero-posterior) and comes out sideways
- Delivery of shoulders: anterior shoulder comes out first, then rest in pelvic axis (i.e. anteriorly)
- Complications: as 1st stage
- Intervene when: maternal/fetal distress, incomplete internal rotation causing failure to progress
- Interventions may include: instrumental delivery/C-section (for fetal distress or failure to progress), oxytocin (for contractions), McRoberts manoeuvre (for shoulder dystocia)
3rd stage of labour (expulsion of placenta)
- Timing: Around 5-10 minutes with syntometrine (30 minutes – 1 hour without) – IM syntometrine is usually given when the head is born to reduce time and post-partum haemorrhage risk
- Signs:
- Gush of blood (50-100ml)
- Lengthening of cord
- Management: controlled cord traction
- Complications:
- Post-partum haemorrhage (>500ml blood loss)
- Primary (within 24 hours) = 4 Ts: Tone (uterine atony), Tissue (retained placenta/clots), Trauma (to perineum), Thrombin (coagulopathy)
- Secondary (24 hours–6 weeks) = retained placenta/clots
- Retained placenta
- Inversion of uterus
- Post-partum haemorrhage (>500ml blood loss)
Other points
- Pelvic anatomy
- Pelvic inlet (brim) formed by: sacral prominence, arcuate and pectineal lines, upper margin of pubic symphysis
- Pelvic outlet formed by: coccyx tip, sacrotuberous ligament, ischial tuberosities, pubic arch
- False (greater) pelvis = part of pelvis above pelvic brim
- True (lesser) pelvis = part of pelvis below pelvic brim
- Female pelvic features (compared to male)
- Wider and shallower
- Round/oval pelvic inlet (male is heart shaped)
- Larger pelvic outlet
- Pubic arch >100˚ (male is <90˚)
- Wider greater sciatic notch
- Curved sacrum
- Common fetal orientations
- Lie:
- Longitudinal (baby vertical)
- Transverse (baby horizontal)
- Oblique (baby diagonal)
- Presentation:
- Cephalic (head is presenting part)
- Breech (bottom is presenting part)
- Position (of occiput relative to pelvic rim):
- Left/right occiput-anterior (LOA/ROA)
- Left/right occiput-transverse (LOT/ROT)
- Left/right occiput-posterior (LOP/ROP)
- Lie:
NB: left occiput-anterior is most common position.
Practice OSCE stations
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