title: Protective effect of intrauterine release of levonorgestrel on pelvic infection: three years' comparative experience of levonorgestrel- and copper-releasing intrauterine devices.
authors.forename: I
authors.initials: I
authors.lastname: Sivin
mesh_terms: D003271:Contraceptive Agents, Female / Q000494:pharmacology*; D005260:Female; D006801:Humans; D007435:Intrauterine Devices, Copper; D016912:Levonorgestrel; D009644:Norgestrel / Q000494:pharmacology*; D000292:Pelvic Inflammatory Disease / Q000517:prevention & control*
chemical_list: D003271:Contraceptive Agents, Female; D009644:Norgestrel; D016912:Levonorgestrel