A reliable assessment of ovulation can be obtained by endometrial biopsy. Endometrial biopsy is performed 2 to 3 days prior to the expected period (although some feel that biopsy done in the midluteal phase is superior for diagnosing luteal phase defects), and the histology is read by the criteria outlined by Noyes, Hertig, and Rock. Although premenstrual biopsy could interrupt a pregnancy if performed in a conception cycle, the danger is not great. An alternative, taking the biopsy on the first day of menses, has three disadvantages:
1. Inconvenient time for patient and physician.
2. The tissue is disrupted and often any more difficult to interpret.
A slight amount of bleeding can occur at the time of the expected period
even if the patient is pregnant.
We recommend the use of the plastic endometrial suction curette. It is easy to use, requires no cervical dilation (3 mm diameter), and is usually painless.