title: Effects of levonorgestrel on ovarian function when used for emergency contraception.
abstract: Recently postcoital treatment with levonorgestrel (LNG) and the antiprogestin mifepristone has emerged as the most effective hormonal methods available for emergency contraception and LNG in a single dose of 1.5 mg has become the recommended emergency contraceptive pill. However, the mechanism(s) of action of these methods when used for emergency contraception in humans remains largely unknown. Taken together available data suggest that emergency contraception with 0.75 mg of LNG twice 12 h apart or a single dose of 1.5 mg of LNG acts mainly to inhibit or delay ovulation. If the effect of emergency contraception is mainly to block the luteinizing hormone surge or to interfere with other processes involved in ovulation is not clear and needs to be further studied. Increased knowledge on mechanism of action could hopefully increase the acceptability, and thus availability of these methods, to offer women a chance to prevent an unwanted pregnancy and thus reduce the numbers of induced abortions.
authors.affiliation: Department of Woman and Child Health, Karolinska University Hospital/Karolinska Institutet, Stockholm, Sweden. kristina.gemzell@kbh.ki.se
authors.forename: K
authors.initials: K
authors.lastname: Gemzell-Danielsson
mesh_terms: D003271:Contraceptive Agents, Female / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006801:Humans; D016912:Levonorgestrel / Q000008:administration & dosage / Q000494:pharmacology*; D010053:Ovary / Q000187:drug effects*; D010060:Ovulation / Q000187:drug effects; D013997:Time Factors
chemical_list: D003271:Contraceptive Agents, Female; D016912:Levonorgestrel