CVS can diagnose hereditary disorder or birth defect in unborn fetus
Chorionic villus sampling (CVS) is a test that can be performed in the first trimester of pregnancy, usually between weeks 10 and 12, to determine chromosomal defects, such as Down syndrome, and congenital deformities such as spina bifida, in the developing fetus. The tissue sampling comes from the placenta where the cells are genetically the same as those of the fetus.
CVS may be offered by your doctor or you can ask about it, especially if there are certain risk factors that could make inherited disorders (e.g., sickle cell disease, cystic fibrosis, Tay-Sachs disease) and defects more likely, such as:
- You are of advanced maternal age, in which case there is an increased risk of birth defects.
- You, or the father of the baby, have a genetic disorder or family history of congenital abnormalities.
- You have given birth to or were previously pregnant with a child who had a birth defect, such as Down syndrome.
- Other test results have indicated abnormality and you want to know more about your baby’s condition.
CVS testing is not given to all pregnant women as there is a one percent chance of miscarriage after the test. The procedure does not diagnose neural tube defects.
How the CVS test is done and understanding the results
This type of test requires careful consideration and thoughtful discussion with your doctor and genetic counselor as well as your partner. The test poses a slight risk to your unborn child and also requires you to be ready for the results. Having CVS testing can help you better prepare for the birth and care of your child, but it can also bring up new questions and concerns for you and your partner to explore.
There are two methods of testing:
- Transcervical – With this method the doctor guides a thin tube into the vagina up through the cervix to the placenta. Sample tissue from the placenta is gently suctioned through the tube.
- Transabdominal – This method involves use of a thin needle (similar to amniocentesis) through the belly to extract the placental cells.
Transcervical is the more common method, but certain factors can determine which approach is best for you and your baby. If you have had recent vaginal bleeding, for example, or an infection (such as herpes), or if your placenta is inaccessible due to uterine fibroids or a tilted uterus, your doctor may prefer the transabdominal approach.
The entire process takes about 30 to 45 minutes. It is not painful though it may be uncomfortable during and after. You may experience symptoms such as cramping or spotting.
It generally takes about seven days to get the results back from the test. In most cases, the results show that everything is normal and your baby has no congenital defects or disorders. If your baby is diagnosed with a congenital abnormality, your doctor will thoroughly explain the results and help you understand your options. In some cases, your baby’s condition can be treated with medication, or with in-utero or postpartum surgery.