If the egg is lucky enough to be fertilized, it will slowly make its way down the uterine tube to the uterus and and eventually prepare itself for implantation. If the egg is not fertilized within 24 hours, it will disintegrate. Immediately following ovulation, both FSH and LH levels drop sharply and remain low until the cycle is repeated the following month. The follicle that is left behind by the released egg is now called the corpus luteum. The corpus luteum begins to produce progesterone immediately following ovulation.
Progesterone helps to soften the lining of the uterus and aid in implantation.
The corpus luteum continues to make progesterone and estrogen for fourteen days following ovulation. If you become pregnant, these two hormones will help maintain the lining of the uterus and help to prevent miscarriage. If no implantation has occurred after the fourteen days, the progesterone and estrogen levels drop rapidly. This drop in progesterone and estrogen levels causes the lining of your uterus to slough off. This sloughing is called menstruation.