A comparison of the inhibition of ovulation achieved by desogestrel 75 μg and levonorgestrel 30 μg daily

A randomized, double blind, group comparative study was performed over a 12 month period to compare inhibition of ovulation during the use of two (progestogen-only) oral contraceptives containing doses of 75 mu g desogestrel or 30 mu g levonorgestrel. Seventy-one female volunteers with regular cycles and established ovulation by ultrasonography and serum progesterone concentrations were recruited from an out-patient clinic in a university hospital and asked to participate in the study. Transvaginal ultrasonography and serum oestradiol, progesterone, luteinizing hormone (LH) and follicle stimulating hormone (FSH) measurements were performed throughout the 7th and 12th 28 day treatment period. Desogestrel at a dose of 75 mu g showed a significant inhibition of ovulation compared to 30 mu g levonorgestrel (P < 0.001).