No abstract available
MeSH terms
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Chorionic Gonadotropin, beta Subunit, Human / blood*
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Chromosomes, Human, Pair 18
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Down Syndrome / diagnosis*
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Female
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Humans
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Maternal Age
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Neck / diagnostic imaging*
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Neck / embryology
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Pregnancy
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Pregnancy Trimester, First
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Pregnancy Trimester, Second
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Pregnancy-Associated Plasma Protein-A / analysis*
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Prenatal Diagnosis / methods*
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Sensitivity and Specificity
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Trisomy / diagnosis
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Ultrasonography, Prenatal
Substances
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Chorionic Gonadotropin, beta Subunit, Human
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Pregnancy-Associated Plasma Protein-A