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Effect of "Missed" Pills on Oral Contraceptive Effectiveness.

Obstetrics & Gynecology: June 1992
Original Article: PDF Only

Objective: The purpose of this study was to determine whether missing pills in an oral contraceptive (OC) cycle resulted in folliculogenesis and eventual ovulation.

Methods: Fifteen women selected from a population requesting tubal reanastomosis were randomized into three groups and issued pill packs missing four consecutive pills in specific sequences, as follows: group I, days 1-4; group II, days 3-6; and group III, days 6-9. Serum was drawn for assay of LH, FSH, estradiol (E2), and progesterone, and serial ovarian ultrasound examinations were done to study follicular development throughout the cycle at 4-day intervals.

Results: No subject ovulated, as suggested by serum progesterone concentrations (not exceeding 0.63 ng/mL for any woman) and ultrasound assessment of follicular development (no follicular diameter exceeding 13 mm). The highest (mean +/- standard deviation) serum concentrations of LH and FSH in any group (13.25 +/- 18.71 and 14.40 +/- 7.71 mIU/mL, respectively) and of E2 (44.35 +/- 26.79 pg/mL) were observed during or immediately after the pill-free interval. Ovarian ultrasound examinations suggested suppressed folliculogenesis in all groups. No functional ovarian cysts were detected.

Conclusions: Oral contraceptives exerted a similar degree of pituitary and ovarian suppression even when the subjects missed four pills at varying times in a cycle. The anovulatory effect persisted when the OC pills were reinstituted and taken reliably after an interval of noncompliance.

(C) 1992 The American College of Obstetricians and Gynecologists