Birth

Birth is the act or process of bearing or bringing forth offspring, at the conclusion of pregnancy.
In mammals, the process involves contraction of the muscular walls of the uterus, expelling the fetus at a developmental stage when it is ready to feed and breathe.
In egg-laying species, the corresponding breakage of and emergence from the egg is known as hatching.
In many cultures, each anniversary of a person's birth or hatching is celebrated as their birthday.