Postcoital treatment with levonorgestrel does not disrupt postfertilization events in the rat

A. L. Müller, C. M. Llados, H. B. Croxatto

Research output: Contribution to journalArticlepeer-review

77 Citations (Scopus)


Levonorgestrel (LNG), a progestin widely used for regular hormonal contraception, is also used for emergency contraception (EC) to prevent pregnancy after unprotected intercourse. However, its mode of action in EC is only partially understood. One unresolved question is whether or not EC prevents pregnancy by interfering with postfertilization events. Here, we report the effects of acute treatment with LNG upon ovulation, fertilization and implantation in the rat. LNG inhibited ovulation totally or partially, depending on the timing of treatment and/or total dose administered, whereas it had no effect on fertilization or implantation when it was administered shortly before or after mating, or before implantation. It is concluded that acute postcoital administration of LNG at doses several-fold higher than those used for EC in women, which are able to inhibit ovulation, had no postfertilization effect that impairs fertility in the rat.

Original languageEnglish
Pages (from-to)415-419
Number of pages5
Issue number5
Publication statusPublished - 1 May 2003


  • Emergency contraception
  • Fertilization
  • Implantation
  • Levonorgestrel
  • Ovulation
  • Rat

ASJC Scopus subject areas

  • Reproductive Medicine
  • Obstetrics and Gynaecology


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