Luteal phase defect is a disruption in the normal female menstrual cycle. The defect occurs when the body does not produce enough of the hormone progesterone. This results in a delay in the development of the lining of uterus (endometrium).

The luteal phase is the time between ovulation and the start of the next menstrual cycle.

The concept of luteal phase defect is controversial, and its role in infertility is uncertain. Luteal phase defects affect about 3 to 4% of women with infertility, and up to 5% in women with a history of repeated miscarriages.

However, luteal phase defects can be found in up to 30% of menstrual cycles of otherwise healthy women.

Risks factors include:

• A history of unexplained infertility
• A history of repeated miscarriages

The main symptom is short or irregular menstrual cycles.

Traditionally, a biopsy of the endometrium is the standard for diagnosing luteal phase defect. However, measuring the progesterone level in blood serum is often used as a means of diagnosis instead of endometrial biopsy due to the pain, difficulties of precise menstrual cycle dating, and expense associated with endometrial biopsy.

A blood serum progesterone level of lower than 10ng/mL one week prior to the start of menstruation or 7 days after the LH (luteinizing hormone) surge is generally accepted as a diagnosis of luteal phase defect.

Progesterone injections or gel (Crinone) are often used when luteal phase defect is suspected.

If there is evidence that low FSH (follicle stimulating hormone) is present with luteal phase defects, clomiphene citrate may also be used.

Using progesterone therapy, success rates of approximately 50% have been reported, but good studies are lacking.