Parturition (labour) is the expulsion of the foetus, placenta and foetal membranes from the uterus. After about 270-280 days in the uterus, the foetus is now prepared to come to the world. The foetus at this stage has turned its head towards the cervix.
Three stages are involved. These are
- dilation stage.
- expulsion stage.
- expulsion of placenta and membrane stage.
1) Dilation stage
The corpus luteum produces a relaxing hormone called relaxin which causes the pelvic ligaments to relax. Also another hormone called oxytocin (pitocin) is secreted from the pituitary gland causing the uterus muscles to contract strongly and regularly resulting in pains.
The cervix expands and the amnion and chorion burst releasing the amniotic fluid to the vagina.
2) Expulsion stage
The contractions of the uterus muscles become frequent and stronger. The cervix and vagina become fully enlarged. The foetus is gradually pushed out from the uterus to the vagina via the cervix and from the vagina to the world. The sudden change in temperature makes the baby to cry for the first time. The cry helps to fill its lungs with air for respiration.
3) Expulsion of placenta and foetal membranes
After the birth of the baby, the uterus muscles continue to contract and the placenta and foetal membranes are forced out as “after-birth”. The umbilical cord connecting the placenta to the baby is cut and tied. The remaining portion dries up and falls off about seven days later. The scar of the healed umbilical cord is called navel.
