Clinical assessment of a low-oestrogen combined oral contraceptive.

A 21-tablet oral contraceptive packet containing .5 mg dl-norgestrel and .03 mg estradiol was clinically tested in 1085 women of reproductive age for a total of 7323 cycles. There was 1 pregnancy which may have been due to incorrect tablet use. 98.2% of the cycles fell within a 28-day plus or minus 3-day pattern. 21% of the women had some breakthrough bleeding at some time, but it was confined to 1 cycle in 63% and not more than 2 cycles in 82%. The contraceptive is recommended for general use on the bases of how pregnancy rate, mean intermenstrual bleeding of .54 days per cycle, and the mean total bleeding of 4.87 days per cycle. The hypothesis that an effective combined oral contraceptive using norgestrel as the progestogen can employ as little as 30 mcg of estrogen is supported.