Incidence of side effects with contraceptive placebo.
147 Mexican women, of low socioeconomic level, who had aborted spontaneously and desired pregnancy, were subjected to trial of placebo oral contraceptive. In 424 months there were 72 pregnancies, a Pearl index of 203.8 pregnancies per 100 couple-years. Menstrual cycles lasted 21-24 days in 30 women (9.8%), 25-35 days in 235 (76.8%), and 36-59 days in 38 (12.4%). 18 cycles (5.8%) were marked by intermenstrual bleeding. Incidence of 31 side effects is listed. Most common were: decreased libido 125 months (29.5%), headache 66 (15.6%), lower abdominal pain and bloating 58 (13.7%), dizziness 47 (11.1%). Common complaints were nervousness, increased libido, dysmenorrhea, nausea, epigastric pain, leg pain, leukorrhea, somnolence. Oral contraceptive-like side effects reported in fewer than 1% of months included acne, mastalgia, increased appetite, weight gain, painful varicose veins. Nausea (here 4.2% of months) was the only side effect with markedly different incidence from other studies with active oral contraceptives.