The luteal phase is the time of a woman's menstrual cycle between ovulation and menstruation. In order for a pregnancy to occur, the luteal phase must be long enough for the uterine lining, or endometrium, to develop to the point where an embryo can implant. If the luteal phase is less than ten days, some doctors say less than 12 days, there is not time for this to happen. This condition is known as a luteal phase defect, also called LPD. The condition can cause early miscarriage and is often associated with infertility. Treatments, including progesterone shots, hormone supplements and fertility drugs, often are effective.
The luteal phase, and thus luteal phase defect, takes its name from the corpus luteum, a structure that develops after ovulation and secretes a hormone called progesterone. It is this hormone that triggers the thickening of the uterine lining and eventually allow for the implantation of an embryo. Progesterone also keeps menses at bay, preventing an early miscarriage. One known cause of the defect is when the corpus luteum stops producing hormones prematurely. In this case, the uterine lining will not fully develop, implantation will be impossible, and menses will begin sooner than normal.
Even if the corpus luteum functions properly and for the right amount of time, a defect can still occur. Sometimes, the uterine lining does not react to the increased levels of progesterone. The result is the same as when the corpus luteum does not perform correctly.
Both of these causes of luteal phase defect occur in the second half of the menstrual cycle. It is also possible for problems with the first half of the cycle to cause or contribute to the phase defect. During this time, the ovaries produces follicles, one of which will later become the corpus luteum. If these follicles do not develop properly, the resulting corpus luteum may also be under-developed, causing it to work improperly.
For women who are not trying to conceive, luteal phase defect is not necessarily a problem, but for those who do want to have a baby, it can be a serious impediment. In general, the only obvious symptom of a defect is the shortened time between ovulation and menstruation. Some women may also notice that their basal body temperature, which normally increases after ovulation, is not consistently higher than their pre-ovulation temperature. Fortunately, there are several medical ways to detect a defect, including strategically timed blood tests to determine progesterone levels, an ultrasound to check the thickness of the uterine lining, or a biopsy of the uterine lining to learn whether its stage of development is consistent with the actual day of the menstrual cycle on which the test is performed.
Once luteal phase defect is diagnosed, it can generally be treated easily and effectively with vitamin B6 supplements, progesterone supplements, or Clomid, a commonly-prescribed fertility drug that enhances progesterone production.