The luteal phase is the second part of the menstrual cycle, which starts with ovulation and ends with menstruation. It is governed by progesterone, so women with issues involving this hormone are often said to have a luteal phase dysfunction, which can lead to infertility and early miscarriage. One of the main causes is the failure of the body to produce quality follicles, which can affect the quality of the corpus luteum. On the other hand, sometimes the corpus luteum itself is to blame, as it does not last long enough. In other cases, the uterine lining is just not thick enough to support implantation of an embryo, despite the proper amount of progesterone.
One cause of luteal phase dysfunction may not even have its roots in the luteal phase, as it may instead involve an issue during the first half of the cycle. During this stage, the body is supposed to make follicle-stimulating hormone, or FSH, but some women do not produce enough. This can lead to poor follicle quality, which in turn compromises the quality of the corpus luteum, as the follicle eventually becomes this element. The result is typically an insufficient amount of progesterone, since the corpus luteum is usually supposed to produce this hormone. The lack of progesterone can cause the period to arrive earlier than it should, and since the uterine lining begins to shed at this point, it is nearly impossible for an embryo to implant.
In some cases, luteal phase dysfunction may occur despite good follicle quality, as the corpus luteum can still fail on its own. If it does not last as long as a healthy corpus luteum should, the progesterone levels drop early, leading to a menstrual period that comes too soon. This may make it difficult to get pregnant since an early period does not leave enough time for an embryo to implant. Even when the embryo is able to start attaching to the uterine wall, a period that arrives too soon can cause it to be flushed out, resulting in a very early miscarriage.
Some women with luteal phase dysfunction actually have quality follicle development, as well as a corpus luteum that lasts for as long as it should. The uterine lining, however, may not respond appropriately to the adequate levels of progesterone that the corpus luteum produces. Thus, the uterine lining is just too thin to support the implantation of an embryo, which of course leads to an early miscarriage. In fact, the miscarriage often occurs so early that the pregnancy is not yet detectable, causing some women with luteal phase dysfunction to believe that they did not conceive at all during the cycle.
