No abstract available
MeSH terms
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Chorionic Gonadotropin, beta Subunit, Human / blood
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Down Syndrome / diagnosis*
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Female
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Humans
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Neck / diagnostic imaging
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Pregnancy
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Pregnancy Trimester, First
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Pregnancy-Associated Plasma Protein-A / analysis
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Prenatal Diagnosis / methods*
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Ultrasonography
Substances
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Chorionic Gonadotropin, beta Subunit, Human
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Pregnancy-Associated Plasma Protein-A