Post-coital administration of levonorgestrel does not interfere with post-fertilization events in the new-world monkey Cebus apella

摘要: BACKGROUND: Experimental evidence to disprove the belief that emergency contraception with levonorgestrel (LNG) prevents pregnancy by interfering post-fertilization events is lacking. Here we determined effect of post-coital and pre-ovulatory administration LNG on fertility ovulation, respectively, in Cebus monkey. METHODS: To determine fertility, 0.75 mg or vehicle were administered orally s.c. once twice within first 24 h after mating occurring very close time ovulation. Females became pregnant aborted mifepristone re-entered study a resting cycle until each 12 females had contributed, randomized order, two vehicle-treated cycles. injected coinciding follicles smaller larger than 5 mm diameter. Six contributed five treated cycles each. RESULTS: The rate was identical vehicle- LNG-treated inhibited delayed ovulation only when treatment coincided follicle <5 CONCLUSION: In monkeys, can inhibit delay but, fertilization has taken place, it cannot prevent establishment pregnancy. These findings do not support hypothesis events.