Final answer:
The hormone produced by the placenta that is pivotal for maintaining pregnancy past the 11th week is progesterone.
Step-by-step explanation:
Hormone Responsible for Maintaining Pregnancy
The hormone produced by the placenta, essential for the maintenance of pregnancy past the 11th week, is progesterone. The corpus luteum, a temporary endocrine structure, initially secretes this hormone, but as pregnancy progresses, particularly after the 11th to 12th week, the placenta takes over the production. Progesterone inhibits uterine contractions, ensuring the protection of the developing fetus. It also maintains the lining of the uterus and suppresses the secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH), preventing new ovarian follicles from developing.
In addition to progesterone, the placenta secretes human chorionic gonadotropin (hCG) and estrogens, which also play crucial roles in maintaining pregnancy and preparing the mother's body for childbirth and lactation. While estrogens increase tissue growth and fetal viability, hCG supports the corpus luteum and influences the secretion of testosterone for the development of the male reproductive system.