title: First-trimester chromosomal analysis of chorionic villi obtained by direct vision technique.
mesh_terms: D002824:Chorionic Villi / Q000648:ultrastructure*; D002877:Chromosomes, Human / Q000648:ultrastructure*; D004314:Down Syndrome / Q000175:diagnosis; D005260:Female; D006801:Humans; D007621:Karyotyping; D008875:Middle Aged; D010920:Placenta / Q000648:ultrastructure*; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011296:Prenatal Diagnosis / Q000379:methods*