Definition of Birth
The birth of puppies, also called the “whelping” of a litter, involves a complex chain of events medically referred to as “parturition.” Parturition is triggered by an even more complex cascade of hormonal changes that encourages the uterus of a pregnant female to expel its contents. Late in pregnancy, when the hormonal systems of the fetuses are relatively mature, the adrenal glands of the puppies and their mother start secreting lots of corticosteroids (so-called “stress hormones”). This causes the placenta’s that are attached to each fetus by its umbilical cord to release a hormone called prostaglandin F2 alpha (PF2). PF2 causes the mother’s ovaries to stop producing progesterone, a hormone that is essential to sustaining her pregnancy. As a result, the mother’s previously tightly-closed cervix relaxes, softens, opens and allows the puppies to exit through the birth canal and come out into the big bold world.