For 96 days prior to baseline sampling, animals were observed for menstrual bleeding and their perineal sex skin swellings were graded. The sex skin swellings were graded on a 1-4 scale, with 1 being no swelling up to 4 being the most swollen. The sex skin swellings are denoted as the columns on the x-axis. Menstrual bleeding is recorded as black dots. Baseline samples included progesterone levels and vaginal biopsies. Biopsies are shown as black triangles and progesterone levels are the solid black line. Progesterone levels were continued for four weeks after COC’s were discontinued. 2-3 biopsies were taken as baselines, three were taken during COC administration and three were taken after COC’s were discontinued. Study day zero is the first day of COC administration. COC’s were given for at least 62 days and no longer than 74 days. The first and last doses are shown on the time line as a dotted line extending from the x-axis. The weights for the animals were: BB173 (7.18kg), BB537 (6.79 kg), BB4800 (5.59kg), BB552 (7.21 kg), BB 269 (6.65 kg), BB4870 (7.54 kg), and BB967 (5.56 kg).