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Cytomegalovirus (Amniotic Fluid)

Does this test have other names?


What is this test?

This test checks the amniotic fluid around a developing baby for cytomegalovirus (CMV). This virus belongs to the herpes family of viruses. The herpes family includes:

  • Herpes simplex

  • Varicella zoster, which causes chickenpox and shingles

  • Epstein-Barr mononucleosis

CMV is common in adults and even children. Most adults will have CMV by the time they're 40. It usually goes undetected because actual symptoms are rare. Most symptoms you could have are relatively mild and flu-like.

Once you contract the virus, you'll always carry it in a dormant, or nonactive, state. Your body will make antibodies to keep the virus in check. CMV can "shed," or make its way into the environment, even without you having any symptoms.

CMV is spread in 2 ways. You can catch it through contact with the bodily fluids of an infected person who's shedding. Or 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. It can pose a health threat in up to 15% of these babies, even if they don't have symptoms at birth.

CMV in a newborn can later lead to:

  • Hearing loss

  • Vision loss

  • Learning disabilities

  • Slightly enlarged liver and spleen

  • Small red spots on the skin

  • Eye problems

  • Seizures

  • Small head size

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%. 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 CMV 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 allow the virus to grow if present.

Why do I need this test?

You may need this test if you are pregnant and have symptoms similar to mononucleosis. Symptoms include:

  • Prolonged fever

  • Sore throat

  • Fatigue

  • Weakness

  • Loss of appetite

  • Achiness

  • Swollen glands

You might also have this test if you have too little amniotic fluid, a possible sign of CMV.

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, such as Down syndrome

  • Genetic disorders like cystic fibrosis

  • Neural tube defects, such as spina bifida

What do my test results mean?

Test results may vary depending on your age, gender, health history, and other things. Your test results may be different depending on the lab used. They may not mean you have a problem. Ask your healthcare provider what your test results mean for you.

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 2 to 3 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 needs 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 exam table. A healthcare provider uses an ultrasound machine that projects an image of your unborn baby onto a monitor. These images pinpoint where to draw the fluid sample from without touching the fetus.

A healthcare provider applies local anesthetic to your belly. They then insert a needle to draw out a small sample of amniotic fluid. Collecting the sample of fluid usually takes only about 5 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. There is also a 1 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 to make sure that the needle is in the correct place.

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 there are any activities you should not do after the procedure.

What might affect my test results?

Taking either antiviral medicines or medicines that suppress your immune system will affect your results. If you take these medicines, you may not be able to have this test.

How do I get ready for this test?

Tell the healthcare provider if you are taking antiviral medicines, even if it's for something common like cold sores. Also tell your healthcare provider about all other medicines, herbs, vitamins, and supplements you are taking. This includes medicines that don't need a prescription and any illegal drugs you may use.

Online Medical Reviewer: Chad Haldeman-Englert MD
Online Medical Reviewer: Raymond Turley Jr PA-C
Online Medical Reviewer: Tara Novick BSN MSN
Date Last Reviewed: 9/1/2022
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