CVS: chorionic villus sampling

CVS or chorionic villus sampling is a diagnostic, prenatal test used to test for chromosomal abnormalities in a fetus between week 10 and week 14 of pregnancy. It is preferred to amniocentesis if you are less than 15 weeks pregnant, but need to check for abnormalities.

In CVS, samples of the chorionic villi (the extensions of the placenta which embed themselves into your uterine lining) are taken from the mother’s uterus and tested in a lab. In week 3, the ball of cells called a zygote splits into two parts: your embryo and the placenta. For this reason the DNA found in the placental tissue will be the same as your baby’s DNA.

CVS can transabdominal (a needle is inserted into your abdomen) or transcervical (a tube is inserted into your cervix). Both methods are relatively short procedures lasting approximately 5 minutes. Most women say that CVS is uncomfortable, not painful. So if you have to get one, don’t worry as you shouldn’t feel too much pain. It is also quite likely that you will experience cramps in your abdomen after CVS, which is completely normal.

Like amniocentesis, CVS is a high risk test that has many possible complications including:

• miscarriage
• infection
• amniotic fluid leakage, which can cause oligohydramnios and hypoplastic lungs
• limb reduction defects

For this reason, only women with high-risk pregnancies should undergo CVS. High-risk pregnancies include thos in which: you have medical history of chromosomal abnormalities, a high-risk AFP test result or if you are over 35. If you have CVS, you should get the first set of results back in a few days and the full set of results in two to three weeks.