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G-banded karyotype of trisomy 21 |
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Prenatal Testing
Prenatal chromosomal analysis can be performed by either chorionic villi sampling (CVS) or amniocentesis. Typically, CVS is performed during the first trimester of pregnancy at 10 to 12 weeks of gestation, while amniocentesis is performed during the second trimester at 14 to 18 weeks of gestation. Percutaneous umbilical blood sampling (PUBS) is a prenatal diagnostic technique that is generally used when fetal blood is the sample of choice. PUBS is performed at 20 weeks of gestation or greater. In addition to karyotype analysis, prenatal FISH is a fast and simple way to determine the sex chromosome complement of the fetus as well as to detect trisomy 13, 18 or 21.
