Which pituitary hormone plays a major role during childbirth?

Oxytocin is the hormone that plays a crucial role during childbirth. It is released by the posterior pituitary gland and is essential for initiating and maintaining labor contractions. During childbirth, oxytocin facilitates uterine contractions, which help in the progression of labor and the delivery of the baby. Additionally, oxytocin promotes maternal bonding and milk ejection during breastfeeding after the birth.

The other hormones listed do not have a direct role in the labor process. Prolactin, while important for lactation, is more involved in milk production rather than in the labor process itself. Follicle Stimulating Hormone is primarily related to reproductive processes such as the maturation of ovarian follicles, and Thyroid Stimulating Hormone is involved in regulating thyroid function but does not have a specific role in childbirth. Thus, oxytocin's functions are pivotal during labor and delivery, making it the correct choice.