An endometrial biopsy is done to diagnose progesterone deficiency or chronic infection (endometritis). The endometrium is the lining of your uterus where the early embryo will implant. Two to four days before the expected date of menses, a small piece of endometrial tissue is obtained and sent to a pathologist for evaluation. You should avoid pregnancy this cycle. The procedure takes 30 seconds and causes brief discomfort.You may take Advil or Motrin one hour before the procedure. Since we consult a pathologist, you will receive a bill from us and from the pathologist.