The endometrial biopsy involves scraping and examining a sample of tissue from the lining of the uterus (endometrium). The procedure makes it possible for the physician to determine if ovulation has occurred, and whether the lining of the uterus has undergone the changes necessary for the implantation of a fertilized egg and the support of an early pregnancy. An endometrial biopsy can also detect an infection or inflammation of the endometrium (endometriosis).
The endometrial biopsy is usually performed one to four days prior to menstruation. In a woman with a 28-day cycle, it is usually scheduled for Days 24 to 26. From start to finish the test takes about five minutes. The physician begins by inserting a speculum into the vagina. The cervical area is cleansed with cotton swabs and antiseptic and an antiseptic solution containing iodine. (The patient must advise the physician if she has an allergy to iodine or shellfish.) An instrument called a tenaculum may be used to stabilize the cervix. This may cause a brief, slight cramping sensation. A narrow plastic instrument is passed into the uterus to collect a small sample of tissue from the side wall of the uterus. During the 60 seconds the tissue is collected minimal to severe cramping may be experienced. This will subside spontaneously after a few minutes.
The tissue is evaluated by a pathologist who will "date" the tissue according to an ideal menstrual cycle. The lining is considered "in-phase" if the progesterone is in a certain range and the lining has thickened to the degree expected on a particular day of the cycle. A biopsy that is "out of phase" suggests a lag in the growth of the lining and an inability of the endometrium to support an early pregnancy. The time frame between Days 24 and 26 of the cycle is too early to perform a pregnancy test. However, a woman undergoing an endometrial biopsy does not need to worry about disturbing a pregnancy. Studies involving large numbers of women who had the procedure performed during the cycles when they conceived showed no greater incidence of birth defects or miscarriage.