Written by Pradeep
There are different kinds of prenatal tests conducted in the course of pregnancy to collect information regarding the health of the mother and fetus. These prenatal tests help to detect the birth defects and health issues regarding the fetus. Prenatal tests include blood tests, ultrasound, urine tests, pap smear, and so on.
While some of these tests are a part of routine pregnancy procedures, others are performed if the mother or the child has a potential risk of developing certain health issues. This article talks about one such prenatal test – chorionic villus sampling.
In This Article
Chorion is a membrane that develops in the course of pregnancy. It is through this membrane the mother connected with the fetus. The chorionic villi, as the name indicates, are small villus or finger-like projection that appears in chorion to increase the contact area with the mother’s blood. The importance of the chorionic villi in pregnancy is that the genetic material in chorionic villus cells and fetal cells are the same. This is because both are developed from the fertile egg.
Chorionic villus sampling (CVS) is a prenatal test performed for detecting chromosomal abnormalities and other inherited disorders and birth defects. In this test, a sample of chorionic villi is removed from the placenta and sent to the lab for genetic analyzing and detecting abnormalities.
CVS is done early in pregnancy(first trimester), and the results are obtained within ten days. If the test results are abnormal, it allows the couple to choose between terminating the pregnancy at the beginning of the pregnancy itself. It is much safer to terminate the pregnancy in the early stage.
Chorionic villus sampling can diagnose most of the chromosomal issues and several hundreds of genetic issues. Some of the commonly searched defects by performing chorionic villus sampling are the down syndrome, cystic fibrosis, Tay-Sachs disease, sickle cell anemia, etc.
Not everybody pregnant should undergo CVS. CVS is performed when the expecting mother has increased chances of having a child with a birth defect or hereditary issue.
The doctor may suggest CVS if:
[Read : Recurrent Miscarriage]
The objective of the procedure of chorionic villus sampling is to collect the cells from the chorionic villus. This is performed 10 to 13 weeks after the last menstrual period by an experienced perinatologist. During this procedure, a thin tube is inserted through the vagina(transcervical).
Alternatively, a long thin needle is put through the abdomen(transabdominal) towards the placenta. The cells are collected into the tube, which is removed slowly and carefully. The whole procedure is assisted by an ultrasound to find the right spot.
After the procedure, the doctor will check the heartbeat of the baby and maternal blood pressure, breathing, etc. to make sure there are no complications.
As in the case of all prenatal tests, CVS also cannot measure the severity of the abnormality. However, the results are highly reliable, as they possess 98% accuracy. One drawback of CVS is that it is not able to detect the neural tube defect of the baby. Sometimes a false positive result is obtained in which abnormal genetic material other than that of the baby is found in the villus. Further tests like amniocentesis are needed to get clarity and confirm the issue.
[Read : Amniocentesis Test During Pregnancy]
Although CVS is a safe procedure, it does have a potential risk as it is an invasive diagnostic test. Miscarriage is the most significant risk associated with this test. It can happen in one out of every hundred CVS performed. Nevertheless, if a very experienced and skilled perinatologist performs the test, it can decrease to one in every 400 procedures.
Other issues that may occur after performing CVS are:
Mostly these issues will resolve on their own in a couple of days. Very rarely CVS can cause:
Amniocentesis, another kind of prenatal test, which is conducted to detect the genetic issues of the fetus, can only be performed around the 16th week of pregnancy. By then, the pregnancy will get into the second trimester, whereas CVS can be performed as earlier as 10 to 13th week of gestation. The result is also obtained faster in CVS than an amniocentesis.
Though minor cramps, spotting, and fluid leakage is common during CVS, but seek immediate medical attention, if the expecting mother experiences:
CVS is not recommended for expecting mothers:
Transcervical CVS is not recommended if the mother has a tilted uterus or have fibroids.
Though CVS has its potential risk, the benefits from the results outweigh the risk. So you can go ahead with the decision of your doctor to perform CVS.