Does Plan B Cause Luteolysis or Luteal Dysfunction to occur?
Plan B decreases circulating levels of progesterone and, possibly, estrogen during the luteal phase of the cycle. The corpus luteum produces a significant amount of progesterone which is important to help prepare the ova to mature and differentiate for implantation to occur but also helps to prepare the lining of the endometrium to accept the ova for implantation where the process of angiogenesis occurs which is the formation of new vascualature, arterioles, glandular structures, and increased permeability of the vasculature. The decrease in progesterone and estrogen partially explains the intermenstrual bleeding that occurs prior to time of the normal menses. The earlier Plan B is used in the cycle (prior to ovulation and the LH surge) there is a higher incidence of intermenstrual bleeding. The earlier Plan B is taken in the menstrual cycle, the greater the chance that the LH surge does not occur. Ovulation and luteal function both depend on the LH surge. Without the LH surge, neither
