No abstract available
MeSH terms
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Adult
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Biomarkers / blood*
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Case-Control Studies
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Chorionic Gonadotropin, beta Subunit, Human / blood*
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Down Syndrome / diagnosis*
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False Positive Reactions
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Female
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Humans
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Predictive Value of Tests
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Pregnancy
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Pregnancy Trimester, First
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Pregnancy-Associated Plasma Protein-A / metabolism
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Prenatal Diagnosis*
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Smoking*
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Ultrasonography, Prenatal
Substances
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Biomarkers
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Chorionic Gonadotropin, beta Subunit, Human
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Pregnancy-Associated Plasma Protein-A