Last reviewed 01/2022

Labour can be somewhat coldly described as process by which the products of conception are expelled from the mother. Natural labour can be thought of as having three components: power, passages, and passengers.

  • power:
    • primary involves uterine contractions
    • secondary involves voluntary muscles of the
    • diaphragm and abdominal walls

  • passages:
    • bony: pelvic bone (see "pelvimetry")
    • soft: uterus, vagina, vulva, supporting tissues

  • passengers: the fetus (see "presentation"), placenta and membranes