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Contraception. 2010 Nov;82(5):404-9. doi: 10.1016/j.contraception.2010.05.004.

Mechanism of action of emergency contraception.

Author information

  • Department of Women's and Children's Health, Division of Obstetrics and Gynecology, Karolinska Institutet/Karolinska University Hospital, S-171 76 Stockholm, Sweden. kristina.gemzell@ki.se

Abstract

A major barrier to the widespread acceptability and use of emergency contraception (EC) are concerns regarding the mechanisms of action of EC methods. Today, levonorgestrel (LNG) in a single dose of 1.5 mg taken within 120 h of an unprotected intercourse is the most widely used EC method worldwide. It has been demonstrated that LNG-EC acts through an effect on follicular development to delay or inhibit ovulation but has no effect once luteinizing hormone has started to increase. Thereafter, LNG-EC cannot prevent ovulation and it does not prevent fertilization or affect the human fallopian tube. LNG-EC has no effect on endometrial development or function. In an in vitro model, it was demonstrated that LNG did not interfere with blastocyst function or implantation.

Copyright © 2010 Elsevier Inc. All rights reserved.

PMID:
20933113
[PubMed - indexed for MEDLINE]
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