Safety and effectiveness of a new low-dose oral contraceptive: a three-year study of 1000 women.

Results of a large-scale study undertaken to evaluate the efficacy and acceptability of a new low-dose oral contraceptive (OC) Ovcan-35 (norethindrone .4 mg and ethinyl estradiol .035 mg) are reported. 1000 women entered the study conducted between October 1972-June 1976 in a family planning clinic in Mexico City. Blood pressure measurements were taken patients recorded bleeding experience and regimen compliance on a calendar pregnancies were analyzed and 143 women agree to endometrial biopsy. For the 3 years of contraceptive use the Pearl index use-effectiveness rate was .28 and method effectiveness rate .21. The dropout rate was 16.6% in the 1st year and 32.1% in the 2nd; most were nonmedical but 37 women discontinued use due to intermenstrual bleeding in the 1st year. 8 women left because of headache 5 in the 1st cycle and 3 discontinued for nausea depression and breast tenderness. There were no blood pressure readings of 149/90 mm Hg or above with blood pressure measured bimonthly for 44 months including those with a history of toxemia. In the 2nd and 4th years posttreatment the endometrial histological examinations showed increases in irregular secretory endometria correlating with lack of amenorrhea. The data suggest that OC use in low more appropriate doses should be reevaluated.