Final answer:
Endometrial health is crucial for pregnancy. Endometriosis disrupts the normal function of the endometrium, increasing the risk of infertility. A regular menstrual cycle involves the natural degeneration of the uterine lining if implantation does not occur.
Step-by-step explanation:
A uterine lining that is unable to support a pregnancy is typically a sign of a condition where the endometrium, the inner lining of the uterus, cannot sufficiently nurture a developing embryo. This can occur if the endometrium does not thicken properly or if there is an underlying condition such as endometriosis, where endometrial cells implant outside the uterus.Endometriosis particularly increases a woman's risk of infertility because these errant endometrial cells can lead to inflammation, formation of scar tissue, and disruptions in the normal anatomy of the reproductive organs.During a normal menstrual cycle, if a fertilized egg is not implanted, the corpus luteum degenerates leading to a decrease in levels of estrogen and progesterone. Subsequently, the endometrium degenerates and is shed during menstruation, initiating the next menstrual cycle.