title: First-trimester biochemical screening for Down syndrome.
mesh_terms: D004314:Down Syndrome / Q000097:blood / Q000175:diagnosis*; D005260:Female; D005315:Fetal Diseases / Q000097:blood / Q000175:diagnosis*; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis