This office procedure involves sampling a small amount of tissue from the endometrium (inside lining of the uterus) shortly before menstruation is due---between 11 and 13 days following ovulation. It should ONLY be performed after a pregnancy test reveals that you are not pregnant. This test can give additional information as to whether a woman has a luteal phase defect. This is a hormonal imbalance that may prevent a woman from sustaining a pregnancy because not enough hormones are produced leading to inadequate functioning of the uterine lining. Because this biopsy does not always provide consistent information and due to uncertainty over appropriate treatments, this tests is not done all the time but only when we feel it provides necessary information. A biopsy may be performed for other reasons as well. In women with irregular or heavy menstrual bleeding a biopsy may be performed to make sure no cancerous or pre-cancerous changes are taking place in the uterus. A biopsy may also be used to check for chronic infection inside the uterine cavity. Results of the biopsy are usually known in 2-3 weeks time.