[A retrospective epidemiological investigation of the contraceptive efficacy of IUDS].
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D001208:Asia; D002681:China; D003267:Contraception; D003906:Developing Countries; D005193:Family Planning Services; D005202:Asia, Eastern; D007434:Intrauterine Devices
Asia; China; Contraception; Contraceptive Methods; Developing Countries; Eastern Asia; Family Planning; Iud; Iud, Unmedicated