Chorionic villus sampling (CVS) is a prenatal test that is used to detect genetic disorders in the baby, usually performed between 10 and 12 weeks of pregnancy.
CVS can provide information about the baby’s chromosomes, genetic disorders, and other problems. It is a safe procedure that carries a low risk of miscarriage. In this blog post, we will discuss the benefits of CVS and how it can help you make informed decisions about your pregnancy.
What is chorionic villus sampling (CVS)?
Chorionic villus sampling (CVS) or chorionic villus biopsy is a prenatal test that can be used to determine if a fetus has certain genetic disorders. It involves taking a small sample of tissue from the placenta, which is then analyzed for signs of genetic and chromosomal abnormalities.
The placenta is a part of the uterus that circulates blood and nutrients from the mother to the baby. The chorionic villi are tiny projections of placental tissue that resemble fingers and contain the same genetic material as the fetus.
CVS can be performed as early as the ninth week of pregnancy, and it carries a very low risk of complications. In most cases, the procedure is performed without any problems, and the mother-to-be can go home the same day.
There are two types of CVS procedures by which samples can be taken:
Transcervical CVS: A small, thin tube called a catheter is inserted through the cervix into the uterus. Guided by ultrasound, the doctor moves the catheter to the area of the placenta that contains the chorionic villi. Once the catheter is in place, a small sample of tissue is removed and sent to the lab for analysis.
Transabdominal CVS: This procedure is performed using a needle that is inserted through the abdomen into the uterus. Guided by ultrasound, a small sample of tissue is removed and sent to the lab for analysis.
Another form of testing that may be used to find genetic and chromosomal disorders is amniocentesis.
Reasons for CVS procedure
Reasons for CVS procedure include:
- To determine if the baby has a genetic disorder such as cystic fibrosis, sickle cell anemia, or Tay Sachs disease
- To determine if the baby has a chromosomal abnormality such as Down syndrome
- If you have a child who has been affected by a genetic disease previously, or if there is a family history of a genetic disease, chromosomal abnormalities, or metabolic disorder.
- You’re 35 or older. The chance of having a chromosomal problem like Down syndrome increases in the baby as women get older.
- Previous ultrasound with questionable or abnormal findings
- Abnormal cell-free DNA test
Chorionic villus sampling cannot detect neural tube defects. If you’re concerned about neural tube defects, an ultrasound or amniocentesis might be advised instead.
Risks of CVS procedure
Risks of the CVS procedure include:
- Miscarriage – The risk of miscarriage is about 0.86% with CVS. This means that out of every 100 women who have CVS, less than one will miscarry as a direct result of the procedure.
- Rh sensitization – Chorionic villus sampling might allow some of the baby’s blood cells to enter your circulation. If you have Rh-negative blood and haven’t developed immunological responses to Rh+ blood, you’ll be given a blood product called Rh immune globulin to prevent your body from forming antibodies against Rh+ blood and damaging the baby’s red blood cells. A blood test can detect if you’ve begun to produce antibodies.
- Infection – There is a very small risk of infection after the CVS procedure.
- Placental abruption – This is a serious complication in which the placenta partially or completely separates from the uterus before delivery.
- Cramping or pain during or after the procedure
- Rupture of membranes – There is a very small risk (less than 0.01%) that the CVS procedure will cause your water to break.
- Preterm labor – There is a very small risk (about 0.04%) that you will go into labor within two weeks after having CVS.
- Allergic reaction to local anesthesia
- Hematoma (bleeding) at the site of the needle insertion
- Cord entanglement – In very rare cases, the umbilical cord can become entangled with the needle used for CVS.
- Limb defects in infants, especially in CVS procedures done before 9 weeks (rare)
CVS is generally considered to be a safe procedure. The chances of complications are very low, and most women who have CVS go on to have a healthy pregnancy and baby. Talk to your doctor about the risks and benefits of CVS to help you make an informed decision.
Benefits of the procedure
The main benefit of CVS is that it can provide parents with information about their fetus’ health before birth.
CVS can also be used to diagnose certain conditions in the fetus, such as chromosomal abnormalities and genetic disorders. This can help parents make decisions about whether or not to continue with the pregnancy, as well as prepare for any special care that the baby may need after birth.
Before the CVS procedure
Before the CVS procedure is performed, the doctor will go over the risks and benefits with you so that you can make an informed decision. If you have any questions or concerns, be sure to ask your doctor or health care provider.
Your health care provider will explain the procedure and ask you to sign a consent form. There are no special dietary or exercise restrictions before chorionic villus sampling.
You will need to have a full bladder for the procedure, so it is important to drink plenty of fluids beforehand.
During the procedure
Chorionic villus sampling is usually performed in an outpatient facility or the health care provider’s office, which means you can go home the same day. The procedure itself takes about 15-20 minutes.
You will be asked to lie on your back on an exam table, with your legs bent and feet in stirrups. Your obstetrician or midwife will apply a special gel to your tummy, then an ultrasound transducer to your baby’s position on a monitor. The ultrasound image will then be used as a guide by your doctor, who will remove a tissue sample from the placenta while you remain motionless.
CVS can be done through your cervix (transcervical) or your abdominal wall (transabdominal).
A speculum will be inserted into your vagina to open it, and a thin, flexible tube called a catheter will be inserted through the cervix into the uterus. The catheter is connected to a syringe that is used to suction out a small sample of chorionic villi.
After cleansing your abdomen with an antiseptic, a needle is inserted through your abdominal wall into the uterus. A small sample of chorionic villi is then removed with a syringe.
After the procedure
Once the tissue sample has been taken, the needle is removed, and pressure is applied to the area to stop any bleeding.
You will then be asked to rest for a few minutes before being discharged. It is important to drink plenty of fluids and avoid strenuous activity for the rest of the day.
You may experience some cramping or spotting after the procedure, which is normal. You should be able to return to your normal activities the next day.
It is important to follow up with your health care provider after CVS to make sure the procedure was successful and there are no complications.
You should also have a follow-up ultrasound to check on the health of your baby. If you have any of the following symptoms, obtain immediate medical attention.
- Fluid leaking from your vagina
- Heavy vaginal bleeding
- Severe pain at the needle insertion site
- Uterine contractions
The results of CVS are usually available within a week. If the test is done early in the pregnancy, you may need to have another test, such as amniocentesis, to confirm the results.
If a chorionic villus sampling test shows that your baby has a chromosomal or genetic condition that can’t be treated, you will have time to prepare emotionally and mentally for the birth, as well as make any necessary arrangements. You may also decide to terminate the pregnancy if you receive a positive result.
CVS is a safe and effective way to test for chromosomal and genetic conditions in the baby. It is important to discuss the risks and benefits with your health care provider before having the procedure.