Chorionic villus sampling

What it is

Chorionic villous sampling, CVS, is one of the invasive procedures of pregnancy. A first trimester scan is indicated during a diagnostic or therapeutic procedure such as chorionic villous sampling, so the scan is part of the procedure and not only a step before it. It is a biopsy of tissue from the villous area of the chorion, derived from the trophoblast, taken transcervically or transabdominally at 10-12 weeks, against amniocentesis, which is done after 15 weeks and draws amniotic fluid whose amniocytes are fetal cells, mostly from fetal skin, grown in culture for chromosomal analysis and DNA studies. Both are the invasive arm of prenatal diagnosis, the detection of abnormalities in the fetus before birth. The non-invasive arm is ultrasonography for anatomical details and nuchal translucency, first and second trimester maternal serum screening, and isolation of fetal cells from the maternal circulation, which can be done from the 10th week and increases with advancing gestational age. Prenatal diagnosis gives couples at risk a range of informed choice, provides reassurance and removes anxiety in high risk groups, allows the option of appropriate psychological, pregnancy, delivery and postnatal management, and can enable prenatal treatment of the fetus.