Once the fetus is fully developed preparations begin for the process of
labour and delivery to birth the fetus.
Preparation for labour
In order for successful
delivery:
As the fetus reaches maturity, the hormone
relaxin causes the
cervix to soften. The fetus also orients itself so that the head is in contact with the
cervix.
The
uterus becomes progressively more excitable due to an increase in
oxytocin receptors in the
uterine lining. The increased excitability causes mild, irregular
contractions called
Braxton-Hicks contractions that are not a part of
labour. If the contractions become regular they may simulate
labour in a process called
false labour.
Stages of labour and delivery
Dilation (6-12 hours)
- The cervix becomes thinner and dilates (increases in diameter) as contractions strengthen; the amion ruptures. Once the diameter of the cervix is forced open to 10 centimetres expulsion can begin.
Expulsion (20-120 min)
- The infant passes through the cervix and vagina as the mother pushes with abdominal muscles
Placental expulsion (15 min)
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1 - Anatomy and Physiology Basics