This 1980 study evaluated the contraceptive efficacy of subcutaneous 17β-estradiol pellet implants in women over 35 years old who could not tolerate oral contraceptives. The regimen involved descending doses (25 mg pellets) implanted at six-month intervals. Over 18,480 cycles (1,540 woman-years), the corrected Pearl Index was 0.273, indicating high contraceptive
