Effectivity and acceptability of oral contraceptives containing natural and artificial estrogens in combination with a gestagen. A controlled double-blind investigation.

With the purpose of investigating effectivity and acceptability of an oral contraceptive containing micronized natural estrogens (estradiol-17 beta 4 mg + estriol 2 mg/norethisterone acetate 3 mg per tablet) versus a contraceptive containing artificial estrogen (ethinyl estradiol 50 micrograms/ norethisterone acetate 3 mg per tablet), a controlled double-blind investigation was performed in 111 young women. The investigation was designed for 12 cycles. The tablets were given consecutively for 3 weeks with 1 week's interruption. In the natural estrogen group 57 women completed 504 cycles, in the artificial estrogen group 54 women completed 510 cycles (Table 1). No pregnancies occurred. There were highly significantly more terminations due to bleeding irregularities (p less than 0.001), and highly significantly more spotting (p less than 0.001), breakthrough (p less than 0.001) and amenorrhea (p less than 0.001) episodes in the natural estrogen group (Tables II and III). Bleeding irregularities on natural estrogens did not subside during the trial (Table IV). There were a few more psychiatric and CNS symptoms on natural estrogen (p less than 0.05), but other side effects did not differ between the two preparations (Table V). Blood pressure and weight did not vary significantly. Despite documented metabolic advantages, the natural estrogen tablet investigated was not found to be clinically acceptable for general usage because of the high incidence of bleeding irregularities. It is conceivable that a change of the estrogen/gestagen ratio, using a variable 3-week schedule, would reduce the number of bleeding irregularities.