Final answer:
True labor contractions are the regular and intensifying contractions that signify the onset of labor, a process divided into three stages: cervical dilation, expulsion of the newborn, and delivery of the afterbirth. These contractions do not lessen with rest or hydration and are a sign that childbirth is beginning.
Step-by-step explanation:
True labor contractions mark the beginning of the process of childbirth, referred to as labor. The physiology of labor is a complex process where several physiological changes occur as a pregnancy progresses into its final weeks. These changes trigger the regular contractions known as true labor, which become more powerful and frequent over time. Labor is the general term for childbirth and is divided into three stages: cervical dilation, expulsion of the newborn, and afterbirth. True labor contractions are regular contractions that do not abate with hydration or rest, indicating the onset of the first stage of labor, which is the dilation of the cervix.
During late pregnancy, physiological changes cause the secretion of hormones that trigger labor. The stretching of the myometrium and cervix by the full-term fetus further stimulates uterine contractions, leading to the progressive dilation and effacement of the cervix. This positive feedback loop encourages the release of oxytocin from the pituitary gland, which in turn triggers even more powerful uterine contractions. As labor progresses, these contractions become more frequent and longer in duration. The three stages of labor culminate in the birth of the baby and the delivery of the placenta.