Chorionic Villus Sampling (CVS)
(CVS, Chorionic Villus Biopsy)
What is chorionic villus sampling?
Chorionic villus sampling (CVS) is a prenatal test that involves taking a sample of
tissue from the placenta to test for chromosomal abnormalities and certain other genetic
problems. The placenta is a structure in the uterus that provides blood and nutrients
from the mother to the fetus.
The chorionic villi are tiny projections of placental tissue that look like fingers
and contain the same genetic material as the fetus. Testing may be available for other
genetic defects and disorders depending on the family history and availability of
lab testing at the time of the procedure.
CVS is usually done between the 10th and 12th weeks of pregnancy. Unlike amniocentesis
(another type of prenatal test), CVS does not provide information on neural tube defects,
myelomeningocele (formerly referred to as spina bifida). For this reason, women who
undergo CVS also need a follow-up blood test between 16 to 18 weeks of their pregnancy
to screen for neural tube defects.
There are 2 types of CVS procedures:
Transcervical. In this procedure, a catheter is inserted through the cervix into the placenta to
obtain the tissue sample.
Transabdominal. In this procedure, a needle is inserted through the belly and uterus into the placenta
to obtain the tissue sample.
Another related procedure that may be used to diagnose genetic and chromosomal defects
Anatomy of the fetus in utero
Amniotic sac. This is a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled
with amniotic fluid (liquid made by the fetus) and the amnion (the membrane that covers
the fetal side of the placenta). This protects the fetus from injury and helps to
regulate the temperature of the fetus.
Anus. This is the opening at the end of the anal canal.
Cervix. This is the lower part of the uterus that projects into the vagina. Made up of mostly
fibrous tissue and muscle, the cervix is circular in shape.
Fetus. This is a term used to describe an unborn baby from the eighth week after fertilization
Placenta. This is an organ, shaped like a flat cake, that only grows during pregnancy and provides
a metabolic interchange between the fetus and mother. (The placenta allows the fetus
to take in oxygen, food, and other substances and eliminates carbon dioxide and other
Umbilical cord. This is a rope-like cord connecting the fetus to the placenta. The umbilical cord
contains 2 arteries and a vein. They carry oxygen and nutrients to the fetus and waste
products away from the fetus.
Uterine wall. This is the wall of the uterus.
Uterus (also called the womb). This is a hollow, pear-shaped organ located in a woman's lower belly, between the
bladder and the rectum. It sheds its lining each month during menstruation and in
which a fertilized egg (ovum) becomes implanted and the fetus develops.
Vagina. This is part of the female genitals sits behind the bladder and in front of the rectum.
It forms a canal extending from the uterus to the vulva.
Reasons for the procedure
Chorionic villus sampling may be used for genetic and chromosome testing in the first
trimester of pregnancy. Reasons that a woman might elect to undergo CVS include:
A previous child with, or family history of, a genetic disease, chromosomal abnormalities,
or metabolic disorder
Maternal age over 35 years by the pregnancy due date
Risk of a sex-linked genetic disease
Previous ultrasound with questionable or abnormal findings
Abnormal cell-free DNA test
There may be other reasons for your healthcare provider to recommend a chorionic villus
Risks of the procedure
As with any invasive procedure, complications may happen. Some possible complications
may include the following:
Cramping, bleeding, or leaking of amniotic fluid (water breaking)
Limb defects in infants, especially in CVS procedures done before 9 weeks (rare)
People who are allergic to or sensitive to medicines or latex should notify their
Women with twins or other multiples will need sampling from each placenta in order
to study each baby.
There may be other risks depending on your specific medical condition. Be sure to
discuss any concerns with your healthcare provider before the procedure.
Certain factors or conditions may interfere with CVS. These factors include, but are
not limited to, the following:
Pregnancy earlier than 7 weeks or later than 13 weeks
Position of the baby, placenta, amount of amniotic fluid, or mother's anatomy
Vaginal or cervical infection
Samples that are inadequate for testing, or that may contain maternal tissue
Before the procedure
The healthcare provider will explain the procedure to you and offer you the opportunity
to ask any questions that you might have about the procedure.
You will be asked to sign a consent form that gives your healthcare provider permission
to do the procedure. Read the form carefully and ask questions if anything is not
Generally, there is no special restriction on diet or activity before chorionic villus
Tell your healthcare provider if you are sensitive to or are allergic to any medicines,
latex, iodine, tape, and anesthetic agents (local and general).
Tell your healthcare provider of all medicines (prescribed and over-the-counter) and
herbal supplements that you are taking.
Tell your healthcare provider if you have a history of bleeding disorders or if you
are taking any anticoagulant (blood-thinning) medicines, aspirin, or any other medicines
that may affect blood clotting. It may be necessary for you to stop these medicines
before the procedure.
Tell your healthcare provider if you are Rh negative. During the CVS procedure, blood
cells from the mother and fetus can mix. This may lead to Rh sensitization and breaking
down of fetal red blood cells. In most cases, prenatal blood tests will have determined
whether you are Rh negative. You may be asked to provide these lab results before
You may or may not be asked to have a full bladder right before the procedure. Depending
on the position of the uterus and placenta, a full or empty bladder may help move
the uterus into a better position for the procedure.
Based on your medical condition, your healthcare provider may request other specific
During the procedure
A CVS procedure may be done on an outpatient basis, or as part of your stay in a hospital.
Procedures may vary depending on your condition and your healthcare provider’s practices.
Generally, a CVS procedure follows this process:
You will be asked to undress completely, or from the waist down, and put on a hospital
You will be asked to lie down on an exam table.
Your vital signs (blood pressure, heart rate, and breathing rate) will be checked.
An ultrasound will be performed to check the fetal heart rate, and the position of
the placenta, fetus, and umbilical cord.
Based on the location of the placenta, the CVS procedure will be performed through
your cervix (transcervical) or through your abdominal wall (transabdominal).
For a transcervical CVS procedure:
The healthcare provider will insert an instrument called a speculum into your vagina
so that he or she can see your cervix.
Your vagina and cervix will be cleansed with an antiseptic solution.
Using ultrasound guidance, a thin tube will be guided through the cervix to the chorionic
Cells will be gently suctioned through the tube into a syringe. You may feel a twinge
or slight cramping. More than one sample may be needed to obtain enough tissue for
The tube will then be removed.
For a transabdominal CVS procedure:
For an abdominal CVS, your belly will be cleansed with an antiseptic. You will be
instructed not to touch the sterile area on your belly during the procedure.
The healthcare provider may inject a local anesthetic to numb the skin. If a local
anesthetic is used, you will feel a needle stick when the anesthetic is injected.
This may cause a brief stinging sensation.
Ultrasound will be used to help guide a long, thin, hollow needle through your belly
and into the uterus and placenta. This may be slightly painful, and you may feel a
cramp as the needle enters the uterus.
Cells will be gently suctioned into a syringe. More than one sample may be needed
to obtain enough tissue for testing.
The needle will then be removed. An adhesive bandage will be placed over the abdominal
needle insertion site.
Procedure completion, both methods:
The fetus’ heart rate and your vital signs will be reassessed.
If you are Rh negative, you may be given Rho(D) immune globulin. This is a specially
developed blood product that can prevent an Rh negative mother's antibodies from reacting
to Rh positive fetal cells.
The chorionic villus tissue will be sent to the lab.
After the procedure
You and your fetus will be monitored for a while after the procedure. Your vital signs
and the fetal heart rate will be checked periodically for an hour or longer.
The CVS tissue will be sent to a specialty genetics lab for analysis. Counseling with
a genetics specialist may be recommended depending on the test results.
You may experience some slight cramping and light spotting for a few hours after CVS.
You should rest at home and avoid strenuous activities for at least 24 hours. You
should not douche or have sexual intercourse for 2 weeks, or until directed by your
Call your healthcare provider to report any of the following:
If a transabdominal procedure was performed, check the bandaged needle site on your
belly for any bleeding or drainage of fluid.
Your healthcare provider may give you additional or alternate instructions after the
procedure, depending on your particular situation.
The content provided here is for informational purposes only, and was not designed
to diagnose or treat a health problem or disease, or replace the professional medical
advice you receive from your healthcare provider. Please talk with your healthcare
provider with any questions or concerns you may have regarding your condition.
This page contains links to other websites with information about this procedure and
related health conditions. We hope you find these sites helpful, but please remember
we do not control or endorse the information presented on these websites, nor do these
sites endorse the information contained here:
American College of Obstetricians and Gynecologists
March of Dimes
National Center on Birth Defects and Developmental Disabilities
National Human Genome Research Institute
National Institutes of Health (NIH)
National Library of Medicine
National Women's Health Information Center