Explain the Birth in human biology?

In humans, birth of the infant occurs about 270 days after conception.

The period during which the uterus contracts to expel the newborn and the placenta is called labor. Sometimes, the first sign of labor is the rupture of the amnion and loss of amniotic fluid. The fluid escapes through the vagina. This is commonly referred to as when someone's "water breaks."

The beginning of labor is triggered by several stimuli. Toward the end of the third trimester of pregnancy, estrogen is produced in larger amounts, stimulating contractions of uterine muscle. The pituitary glands of both mother and fetus secrete oxytocin, that also stimulates uterine contraction. During this stage of labor, uterine contractions pull the cervix open (dilation) until it is large enough to allow the baby to pass through.

During the second stage, the baby's head moves into the vagina and is visible from the outside. As soon as the baby is out of the birth canal, it can breathe and can be independent of the mother's circulation, which is when the umbilical cord can be clamped and cut. The placenta and fetal membranes are expelled a few minutes to an hour after birth.