women s health issues
Menstrual Cycle
Luteal phase
The luteal phase begins after ovulation. It lasts about 14 days (unless fertilization occurs) and ends just before a menstrual period. In this phase, the ruptured follicle closes after releasing the egg and forms a structure called a corpus luteum, which produces increasing quantities ofprogesterone. Theprogesteroneproduced by the corpus luteum does the following: Prepares the uterus in case an embryo is implanted Causes the endometrium to thicken, filling with fluids and nutrients to nourish a potential embryo Causes the mucus in the cervix to thicken, so that sperm or bacteria are less likely to enter the uterus Causes basal body temperature to increase slightly during the luteal phase and remain elevated until a menstrual period begins (this increase in temperature can be used Overview of Infertility ) During most of the luteal phase, theestrogenlevel is high.Estrogenalso stimulates the endometrium to thicken. The increase inestrogenandprogesteronelevels causes milk ducts in the breasts to widen (dilate). As a result, the breasts may swell and become tender. If the egg is not fertilized or if the fertilized egg does not implant, the corpus luteum degenerates after 14 days, levels ofestrogenandprogesteronedecrease, and a new menstrual cycle begins. If the embryo is implanted, the cells around the developing embryo begin to produce a hormone called human chorionic gonadotropin. This hormone maintains the corpus luteum, which continues to produceprogesterone, until the growing fetus can produce its own hormones. Pregnancy tests are based on detecting an increase in the human chorionic gonadotropin level. 