This is an ovulation disorder that could result in the inability to conceive. The luteal phase is that part of the cycle between ovulation and start of the next cycle. The ideal length of the phase is about 11 to 16 days. However, when this is considerably shorter, it negatively impacts the ability of the fertilized egg to implant in the uterine wall. In this case, such a fertilized egg is lost during menstruation. Unfortunately, many woman with this condition remain unaware that conception ever occurred.
It can be diagnosed through a biopsy of the uterine lining, testing for serum progesterone (seven days after ovulation. Levels below 14 are not adequate for ovulation), estradiol (done midcycle), and follicle size (by ultrasound, also midcycle).
The luteal phase defect can be treated by clomid and other injectable fertility drugs, progesterone supplements (after ovulation), also hCG injections.