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Pregnancy
Gestational Age
Down's Syndrome
Fetal Diseases
Trisomy
Second Pregnancy Trimester
Biological Markers
First Pregnancy Trimester
Maternal Age
Prenatal Diagnosis
Case Control Studies
Mass Screening
Chorionic Gonadotropin
Estriol
Inhibins
alpha-Fetoproteins
beta Subunit Human Chorionic Gonadotropin
Activins
Pregnancy-Associated Plasma Protein-A
Chromosomes, Human, Pair 18
Co-Publications
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44
19
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9
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