A luteal phase defect is a disruption in a woman's monthly menstrual cycle.
The luteal phase is one stage of the menstrual cycle. It occurs after ovulation (when the ovaries release an egg) and before your period starts.
During this phase, the lining of your uterus normally becomes thicker to prepare for a possible pregnancy.
If you have a luteal phase defect, the lining of your uterus does not grow properly each month. This can make it difficult to become or remain pregnant.
A luteal phase defect may also be called an "inadequate luteal phase" or an abnormality in endometrial development.