A randomized double-blind trial of two low dose combined oral contraceptives.

Fifty-five women using Loestrin-20 (20 microgram ethinyl oestradiol and 1 mg norethisterone acetate) as an oral contraceptive have been compared with a like number using Microgynon-30 (30 microgram ethinyl oestradiol and 150 microgram levonorgestrel) in a randomized, double-blind trial. Despite the small sample size, the main finding in the trial is clear-cut; Loestrin-20 provides poor cycle control and is thus less acceptable as an oral contraceptive than Microgynon-30. Although there is also a suggestion that Loestrin-20 may be less effective than Microgynon-30, the difference in the accidental pregnancy rates is not statistically significant.