Cytomegalovirus (Amniotic Fluid)
Does this test have other names?
What is this test?
This test checks a developing baby for cytomegalovirus (CMV), a virus that belongs
to the herpes family of viruses. The herpes family includes herpes simplex; varicella
zoster, which causes chickenpox and shingles; and Epstein-Barr mononucleosis.
Cytomegalovirus is common in adults and even children. The majority percent of all
adults will have CMV by the time they're 40. It usually goes undetected because actual
symptoms are rare. Most symptoms you could experience are relatively mild and flu-like.
Once you contract the virus, you'll always carry it in a dormant, or nonactive, state
and produce antibodies to keep the virus in check. CMV can "shed," or makes its way
into the environment, even without your having any symptoms.
CMV is spread in two ways. You can catch it through contact with the bodily fluids
of an infected person who's shedding, and it can be transferred from a woman to her
unborn baby during pregnancy or childbirth, and to her newborn while breastfeeding.
The greatest concern is when a woman contracts CMV for the first time during pregnancy.
The infection is passed to the baby about one-third to one-half of the time and can
pose a health threat in up to 15 percent of these babies, even if they don't have
symptoms at birth.
CMV in a newborn can later lead to:
If you had CMV before becoming pregnant and it becomes active again, you could still
infect your unborn baby, but the chances are much lower—only about 1 percent. Of those
infected babies, only a small portion will have symptoms at birth, or go on to develop
CMV disease symptoms.
Healthcare providers can check for cytomegalovirus in several ways. To check for it
in an unborn baby, the test is done on amniotic fluid, the fluid in the amniotic sac,
where the baby is developing. The procedure used to get a sample of amniotic fluid
is called amniocentesis. The amniotic sample will be put in a special dish with a
substance that will encourage the virus to grow, if it exists in the sample.
Why do I need this test?
You might need this test if you are pregnant and have symptoms similar to mononucleosis.
You might also have this test if you have too little amniotic fluid, a possible sign
What other tests might I have along with this test?
Your healthcare provider may also order other tests of your amniotic fluid. The fluid
can be checked for other serious health conditions, including chromosome abnormalities
that could mean Down syndrome, genetic disorders like cystic fibrosis, and neural
tube defects such as spina bifida.
What do my test results mean?
Many things may affect your lab test results. These include the method each lab uses
to do the test. Even if your test results are different from the normal value, you
may not have a problem. To learn what the results mean for you, talk with your healthcare
Normal results are negative, meaning that CMV wasn't found. Positive results mean
that your developing baby has been exposed to CMV.
If your results are positive, your newborn will be given either a saliva swab or urine
culture test within the first two to three weeks of life. If your newborn tests positive
for CMV, your child's healthcare provider will closely watch the baby's hearing, vision,
and brain development. You may also want to discuss the possibility of antiviral medicines
for the infant.
How is this test done?
This test requires a sample of amniotic fluid. The sample is collected during a procedure
called amniocentesis. It is usually done in a medical office.
In this procedure you lie down on an examination table, and a healthcare professional
uses an ultrasound machine project an image of your unborn baby onto a monitor. These
images pinpoint where to draw the fluid sample without touching the fetus.
A healthcare provider applies local anesthetic to your abdomen then injects a needle
to draw out a small sample of amniotic fluid. Collecting the sample of fluid usually
only takes about five minutes, but you may be at the facility for 45 minutes or longer.
Does this test pose any risks?
Amniocentesis is considered a safe procedure. There is a small risk of fluid leakage
from your vagina. You have a one in 400 chance that you may miscarry. Miscarriages
can happen if you develop an infection in your uterus, if your water breaks prematurely,
or if you go into early labor.
It's extremely rare for the baby to come into contact with the needle. The healthcare
providers watch the monitor very closely.
After the procedure, you may feel cramping, leak a little fluid or blood from your
vagina, or feel discomfort around the puncture site. If any of these symptoms persist
or get worse, or if you develop a fever, call your healthcare provider right away.
Ask your healthcare provider if you should avoid certain activities after the procedure.
What might affect my test results?
Taking either antiviral medicines or medicines that suppress your immune system will
affect your results. Because of this, if you take these medicines, you may not be
able to have this test.
How do I get ready for this test?
Make sure to tell the healthcare provider if you are taking antiviral medicines, even
if it's for something common like cold sores. In addition, be sure your healthcare
provider knows about all other medicines, herbs, vitamins, and supplements you are
taking. This includes medicines that don't need a prescription and any illicit drugs
you may use.