Parturition (Birth) in Human

After nine months of pregnancy, the fully developed foetus is ready for delivery. The process of childbirth is called parturition.

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Parturition is the act of expelling the full term foetus from the mother's uterus at the end of gestation.

• Humans are viviparous - they give birth to live young ones (as opposed to oviparous organisms that lay eggs).
• The time from fertilisation/conception to birth is called the gestation period.
• In humans, the gestation period is approximately 9 months (280 days / ~38 weeks).
• Throughout pregnancy, the uterus undergoes periodic episodes of weak contractions called Braxton-Hicks contractions - these are sometimes mistaken for real labour (false labour).
• As pregnancy progresses, rising oestrogen concentration promotes stronger uterine contractions near term.

Parturition is induced by a complex neuroendocrine mechanism - it involves a cascade of hormonal signals that build upon each other in a positive feedback loop.

Step-by-Step Sequence: Parturition Mechanism

Parturition

The entire process of parturition (labour) is divided into three distinct stages:

• Parturition is the process of childbirth, i.e., the delivery of the foetus at the end of the gestation period.
• It is controlled by a neuro-endocrine mechanism involving signals from the fully developed foetus and placenta.
• Foetal signals trigger uterine contractions known as the foetal-ejection reflex (labour pain).
• Hormones like ACTH and corticosteroids from the foetus stimulate the release of oxytocin from the mother’s pituitary gland.
• Parturition occurs in three stages: dilation, expulsion of the baby, and after birth (placenta removal).