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).
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)
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