The progesterone and oestradiol continue the hypertrophy of endometrial lining in the uterus and fallopian tubes and maintain it throughout pregnancy. progesterone is also necessary for the proper implantation of the foetus in the uterine wall. It stimulates the endometrial glands to secrete a nutrient fluid for the foetus, hence the term secretory phase. The progesterone inhibits the release of FSH so that it may not develop additional follicles and eggs.
Related Theory
There is no menstrual cycle during pregnancy due to the secretion of progesterone hormone by the corpus luteum. The progesterone hormone inhibits the production of the gonadotropic hormones from the pituitary and prevents the uterine lining from sloughing and supports pregnancy.