title: [Mechanisms of action of emergency contraception].
abstract: There is still controversy regarding the mechanism of action of levonorgestrel (LNG) for emergency contraception (EC). For those who state that pregnancy starts prior to implantation, any compound able to interfere with post-fertilization and pre-implantation stages, should be considered as abortifacient. Previous research suggests that EC in humans acts predominantly after fertilization. Current evidence with LNG-only EC supports a pre-fertilization mechanisms to explain its action. There are many potential mechanisms of action, which could vary pending on the day during the fertilization window of the ovarian cycle at which the contraceptive is given. This paper reviews the evidence for each potential mechanism of action. According to the most recently statements, it is concluded that the primary and possible the only mechanism of action of LNG-only EC is preventing or delaying ovulation.
authors: Departamento de Biología de la Reproducción, Instituto Nacional de Ciencias Médicas y Nutrición Salvador Zubirán, México, DF.
authors: Marta
authors: M
authors: Durand
authors: Fernando
authors: F
authors: Larrea
authors: Raffaela
authors: R
authors: Schiavon
mesh_terms: D000818:Animals; D044363:Contraception, Postcoital; D003281:Contraceptives, Postcoital / Q000494:pharmacology*; D005260:Female; D006801:Humans; D023421:Models, Animal
chemical_list: D003281:Contraceptives, Postcoital