02 April 2014

#118 Process of birth

Birth begins when the strong muscles in the wall of the uterus start to contract. This first stage of birth (called labour) is triggered by the hormone oxytocin.

Stages of birth 

 Stage 1
  • The muscular walls of the uterus start to contract ---> slowly stretch the opening of the cervix
  • The pressure breaks the amniotic sac, releasing the amniotic fluid.
  • Contraction gradually become more frequent, pushing the baby down towards the cervix, which become dilated to allow baby to pass through.

Stage 2

The vagina stretches to allow the baby to be born.

Stage 3

The baby is still attached to the placenta by the umbilical cord, so this is cut and tied. The placenta breaks away form the wall of the uterus and passed out (afterbirth). 

Try this

Describe, in sequence the main events which occur during birth. [3 marks]


Three points from:
  • the wall of the uterus contracts
  • the amniotic sac bursts
  • amniotic fluid passes out though the vagina
  • the cervix dilates
  • the baby passes out through the cervix and vagina. 

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