Luteal Phase Defect

Couples who are struggling to conceive may believe that a normal menstrual cycle indicates the woman’s reproductive system is functioning properly and they may therefore look elsewhere for the problem. However, a condition called a luteal phase defect can impair fertility without disturbing the menstrual cycle.

Endometrial lining

The lining of the uterus, called the endometrium, is an essential component of early pregnancy. After the egg is fertilized it has to implant into the endometrium in order to begin development. If the lining is not properly developed, the egg cannot implant. The lining grows in response to estrogen during the first half of the menstrual cycle, and then develops to prepare to receive an egg in response to progesterone secreted by the follicle after it ruptures around day 12-14. The second half of the menstrual cycle following ovulation is called the luteal phase.

Luteal Phase Defect

In women affected by luteal phase defects, the endometrium begins to develop later than usual, either due to insufficient progesterone being secreted or due to a lack of response of the endometrium to the hormone. As a result, it is not fully developed by the time the fertilized egg arrives, and the egg cannot implant. The menstrual cycle proceeds as it normally would if fertilization had not occurred.


Women who have a normal menstrual cycle but are struggling to conceive can be tested for a luteal phase defect using a biopsy of the endometrium. A day or two before menstruation is expected, a sample is taken of the endometrium. Its appearance and phase of development is assessed. If its stage of development is not in phase with the woman’s menstrual cycle, a luteal phase defect is occurring. Because all women occasionally experience luteal phase defects, the test needs to be repeated on the next menstrual cycle to confirm a chronic luteal phase defect problem is occurring.


Once a luteal phase defect has been confirmed, there are several options for treatment. One is to take supplemental progesterone after ovulation, either by injection or orally. Another option is to take supplemental human chorionic gonadotropins to stimulate the ruptured follicle to secrete more progesterone. The third option is to take drugs or hormones to stimulate the development of multiple follicles, which together will then produce additional progesterone. After treatment, most women are able to conceive naturally.