The corpus luteum is a temporary endocrine gland in the ovary necessary for the production of progesterone to prepare the endometrium (lining of the uterus) for implantation of a fertilized egg (blastocyst) and sustain pregnancy. The corpus luteum maintains a healthy and nutritional endometrial environment during embryonic development until the placenta is developed enough to produce progesterone in sufficient quantities to take over the maintenance of pregnancy. If the amount of progesterone secreted by the corpus luteum is insufficient or continues for too short a period, the developing fetus is unlikely to survive. This is called a luteal phase defect (LPD).

The corpus luteum—literally translated as yellow body—is actually the remnant of a follicle, a protective group of special cells which surrounds each individual oocyte housed within the ovaries. The metamorphosis from follicle to corpus luteum takes place immediately following the ovulation...