Contraception in general practice before teenage pregnancy. Inappropriate selection of cases and controls biased study.
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Leung
D000293:Adolescent; D016022:Case-Control Studies; D003267:Contraception; D004739:England; D005194:Family Practice / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data*; D011247:Pregnancy; D011253:Pregnancy in Adolescence / Q000517:prevention & control*; D015983:Selection Bias