from where do signals of parturition originate and what does maternal pituitary release for stimulating uterine contractions for child birth?
The signals for parturition originates from fully developed foetus and placenta which induce mild uterine contraction. This triggers release of oxytocin (birth hormone) from the maternal pituitary gland. The oxytocin starts a series of powerful contractions in the uterus to help expel the baby and limits bleeding of the placenta near the entry of the vaginal canal.
They come from the mother's brain. The Mother's brain closely monitors the development of a child and when it feelsthe baby's ready for , it (Mother's brain) sends out the parturition signals and result in labour and subsequently delivery, although parturition can also be artifically induced by many factors, with the most common reason being health concerns of the mother the child (like in cases when the mother crosses the due delivery date without delivery.)
Oxytocin, a hormone produced in females, stimulates the uterine muscles. A subsequent increase in the level of Oxytocin results in vigrous contraction of the uterine muscles, forcing the individual out, thus causing a natural birth.