Final answer:
Progesterone is the hormone that maintains the uterine lining growth for embryo implantation, secreted by the corpus luteum after ovulation.
Step-by-step explanation:
The hormone responsible for maintaining the growth of the uterine lining in preparation for a fertilized egg is progesterone. This hormone is secreted by the corpus luteum after ovulation occurs. Progesterone's role is crucial as it not only encourages the thickening of the endometrium, creating a nurturing environment for an embryo, but it also prevents the contraction of uterine muscles to maintain pregnancy, suppresses the formation of new ovarian follicles, and inhibits the release of FSH and LH to ensure that no other follicles will mature during pregnancy.