Hormone which is not useful for parturition is

Prolactin stimulates milk production.

The onset of labor is determined by complex interactions of several placental and fetal hormones. Toward the end of gestation, the rise in estrogens results from increasing secretion by the placenta of corticotropin releasing hormone, which stimulates the anterior pituitary gland of the fetus to secrete ACTH (adrenocorticotropic hormone). In turn, ACTH stimulates the fetal adrenal gland to secrete cortisol and dehydroepiandrosterone (DHEA), the major adrenal androgen. The placenta then converts DHEA into an estrogen. High levels of estrogens cause the number of receptors for oxytocin on uterine muscle fibers to increase, and cause uterine muscle fibers to form gap junctions with one another. Oxytocin released by the posterior pituitary stimulates uterine contractions, and relaxin from the placenta assists by increasing the flexibility of the pubic symphysis and helping dilate the uterine cervix. the placenta to release prostaglandins, which induce production of enzymes that digest collagen fibers in the cervix, causing it to soften. Estrogen also stimulates the placenta to release prostaglandins, which induce production of enzymes that digest collagen fibers in the cervix, causing it to soften. Contractions of the uterine myometrium force the baby’s head or body into the cervix, distending (stretching) the cervix causing ejection.