9. Labour and Birth

9.1: Preparation for Labour

9.1.1 Cervical Ripening

  • Mediated by:
    • Prostaglandins
    • Relaxin
    • Estrogen

9.1.2 Uterine Activation

  • Increase in:
    • Oxytocin receptors
    • Gap junctions
    • Prostaglandin synthesis

9.2 Stages of Labour

Stage 1: Cervical Dilation

  • Latent phase → gradual dilation
  • Active phase → rapid dilation (6–10 cm)

Stage 2: Expulsion

  • From full dilation to delivery of baby
  • Strong, regular contractions

Stage 3: Placental Delivery

  • Separation and delivery of placenta
  • Uterine contraction minimizes bleeding

9.3 Mechanisms of Labour

  • Fetal descent
  • Flexion
  • Internal rotation
  • Extension
  • External rotation
  • Expulsion

9.4 Pain in Labour

  • First stage: visceral pain (T10–L1)
  • Second stage: somatic pain (pudendal nerve)