Which hormone is primarily responsible for uterine contractions during labor?

Oxytocin is the hormone primarily responsible for stimulating uterine contractions during labor. It is produced by the hypothalamus and released by the posterior pituitary gland. During labor, oxytocin facilitates rhythmic contractions of the uterus, which help in dilating the cervix and pushing the baby through the birth canal. The release of oxytocin not only initiates labor but also increases the intensity and frequency of contractions as labor progresses.

In contrast, progesterone plays a role in maintaining pregnancy by relaxing the uterine muscles and preventing contractions before labor begins. Prolactin is mainly involved in milk production after childbirth and does not have a direct role in labor contractions. Relaxin helps to soften the cervix and pelvis in preparation for birth but does not cause contractions. This hormonal interplay is essential for a successful labor and delivery process.