Final answer:
Progesterone is the hormone essential for maintaining pregnancy. It inhibits new ovarian follicles and suppresses uterine contractions, and the placenta continues its secretion throughout pregnancy.
Step-by-step explanation:
The hormone essential for maintaining pregnancy is Progesterone. Progesterone prevents the development of new ovarian follicles and suppresses uterine contractions, which is crucial for maintaining a successful pregnancy. During the initial stages of pregnancy, the corpus luteum secretes progesterone which stimulates the production of decidual cells that nourish the early embryo. As the pregnancy progresses, the placenta takes over the secretion of progesterone and continues to be the primary source of this essential hormone throughout the rest of the pregnancy. Although estrogens and human chorionic gonadotropin (hCG) also play significant roles in pregnancy, with estrogens contributing to the stimulation of tissue growth and hCG supporting progesterone synthesis, it is progesterone that is primary in maintaining the pregnancy.