The amount of mucous increases and it becomes clear and thin. This facilitates conception by aiding the passage of sperm through the cervical canal. Sperm can live for up to 72 hours in the female reproductive system. The corpus luteum remains intact for the remainder of the cycle. Progesterone causes the endometrial lining to become secretory and nutritive in anticipation of implantation of a fertilized egg.
Progesterone also inhibits the contractions of smooth muscle cells of the myometrium.
The breast swelling, tenderness and pain experience by some women is most likely due to the effects of progesterone on breast tissue. The detection of hCG in urine is the basis of laboratory and home pregnancy tests. If fertilization and implantation have occurred, than the corpus luteum will be stimulated by hCG to continue its production of estrogen and progesterone to maintain the pregnancy. This is important because the corpus luteum dies 14-22 days after ovulation if fertilization and implantation do not occur. The coiled arteries serving the endometrial lining contract, causing ischemia leading to tissue death in the functionalis.