Subjects will return to the center during the mid-luteal phase for a pelvic ultrasound and blood sample for local and central progesterone on day 6 or 7 after the LH surge, and will also return for a repeat blood sample for progesterone on day 8 or 9 after the LH surge. Ovulation will be confirmed by a progesterone level ³ 10 ng/mL. If the results of the progesterone test indicate that the patient has not ovulated, the subject will be brought back one to two days later for a repeat progesterone test.