Lab result explainedInflammationLast updated November 11, 2026

CMV IgG and IgM: what positive and negative cytomegalovirus antibody results and avidity mean

CMV IgG and IgM (CMV antibodies) · CMV antibody panel (IgG and IgM), with IgG avidity when IgM is positive; CMV PCR for current viral activity · reported in IgG and IgM: negative, equivocal or positive, with an index, AU/mL or IU/mL that varies by assay; IgG avidity: percentage or low/intermediate/high

Cytomegalovirus (CMV) is a common herpes-family virus that about half of US adults have caught by age 40, usually without noticing, and that then stays in the body for life in a dormant state. The CMV antibody test measures two antibodies against it. CMV IgG appears a few weeks after the first infection and stays positive for life, so a positive IgG means you have had CMV at some point and carry it. CMV IgM appears within the first week or two of a new infection and usually fades over 3 to 6 months, so it is used as a marker of recent infection, though it is a much less reliable one than most people assume.

For a healthy adult, CMV status rarely matters, which is why the test is usually ordered in three specific situations. In pregnancy, a first (primary) CMV infection can pass to the baby in about 30 to 40 percent of cases and is the leading infectious cause of hearing loss and developmental problems in children, affecting about 1 in 200 births; the question is whether an infection happened recently, and that is where IgM and IgG avidity come in. Before organ or stem-cell transplant, the donor's and recipient's IgG status predict the risk of CMV disease after transplant and decide preventive treatment. And in someone with a mononucleosis-like illness whose mono test is negative, CMV serology can identify the cause.

The result that causes most worry is a positive IgM. A positive CMV IgM in a person with a positive IgG can mean a recent primary infection, a reactivation of old infection, or, very often, nothing at all: IgM tests cross-react with Epstein-Barr virus and other infections, pick up rheumatoid factor, and can stay positive for a year or more after a genuine infection. The IgG avidity test resolves this by measuring how tightly the IgG binds: low avidity means the infection was within the past 3 to 4 months, high avidity means it was older. For a pregnant person, a positive IgG with negative IgM, or a positive IgM with high avidity before about 16 weeks, is reassuring; a low-avidity result in early pregnancy is the pattern that leads to specialist referral.

CMV antibodies at a glance

What it is: blood antibodies to cytomegalovirus. IgG positive = past infection, lifelong carriage; IgM positive = possible recent infection, but often false positive or persistent.
IgG positive, IgM negative: past infection, no recent primary infection. About 50 to 60 percent of US adults; immune in the ordinary sense, though reactivation and reinfection are possible.
IgG negative, IgM negative: never infected (seronegative). In pregnancy, susceptible to a primary infection; in transplant, at highest risk if the donor is positive.
IgG positive and IgM positive: needs an IgG avidity test. Low avidity (below about 30 to 40 percent) = infection within the last 3 to 4 months; high avidity (above about 60 percent) = older infection; cutoffs are assay-specific.
IgG negative, IgM positive: either very early infection (IgG appears within 1 to 3 weeks; repeat in 2 to 3 weeks) or a false-positive IgM, which is the more common explanation in a well person.
Nothing you eat or take changes CMV antibodies. In pregnancy, hygiene around young children's saliva and urine lowers the chance of a primary infection; in transplant, serostatus guides antiviral prevention.

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What CMV antibodies measures

CMV spreads through saliva, urine, breast milk, sexual contact, blood transfusion and transplanted organs. Young children in daycare shed it in saliva and urine for months to years, which is why parents and childcare workers are the adults most likely to catch it. After the first infection the virus settles into white blood cells and other tissues for life, reactivating from time to time, usually silently. The immunoassays measure IgG and IgM antibodies against viral proteins and report each as negative, equivocal or positive with a numeric index, arbitrary units (AU/mL) or international units (IU/mL), whose cutoffs differ between manufacturers; the printed interpretation is what counts, not the number.

IgG becomes detectable 1 to 3 weeks after infection and is positive for life, so it is the test of whether you have ever been infected. IgM appears in the first days of a primary infection, peaks over a few weeks, and typically disappears by 3 to 6 months, but in 10 to 30 percent of people it persists for 9 to 12 months or longer, it can reappear during reactivation or reinfection with a different strain, and it cross-reacts with antibodies to Epstein-Barr virus, parvovirus B19 and other viruses and with rheumatoid factor. In a low-risk population, a majority of positive IgM results in people who feel well are not primary infections.

IgG avidity measures the strength with which IgG binds the virus. Early antibodies bind weakly; over 3 to 4 months the immune system refines them and avidity rises. The lab reports a percentage (the fraction of antibody that stays bound when a protein-denaturing agent is added) or a category. Low avidity indicates a primary infection within roughly the previous 3 to 4 months, high avidity excludes one in that window, and intermediate results are indeterminate. Avidity is most useful in the first 16 to 18 weeks of pregnancy, when a high result rules out infection around conception and the first trimester, the period of greatest fetal risk. Separately, CMV PCR on blood, urine, saliva or amniotic fluid detects the virus itself and is the test of active infection in transplant recipients, fetuses and newborns.

Normal range for CMV antibodies

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

Group	Typical range (IgG and IgM: negative, equivocal or positive, with an index, AU/mL or IU/mL that varies by assay; IgG avidity: percentage or low/intermediate/high)	Notes
IgG negative	Below the assay cutoff (seronegative)	Never infected, or within the first 1 to 3 weeks of a primary infection. Susceptible to primary infection; in pregnancy this is the group hygiene counseling targets, and in transplant the group at highest risk if the donor is IgG positive.
IgG positive	Above the assay cutoff (seropositive)	Past infection and lifelong carriage; found in about 50 to 60 percent of US adults overall, 35 to 40 percent of young adults and 90 percent or more of people over 80. A high IgG number does not mean recent or active infection.
IgG equivocal	Within the assay's gray zone	Usually very early seroconversion or non-specific binding. Repeat in 2 to 3 weeks; a clear rise confirms recent infection.
IgM negative	Below the assay cutoff	No serologic evidence of recent primary infection. IgM can be negative in the first few days of infection and in immunosuppressed people.
IgM positive	Above the assay cutoff	Recent primary infection, reactivation or reinfection, or (commonly) a false positive from cross-reacting antibodies or persistent IgM. Needs IgG avidity if IgG is positive, or a repeat IgG in 2 to 3 weeks if IgG is negative.
IgG avidity, low	Below about 30 to 40 percent (assay-specific)	Primary infection within approximately the previous 3 to 4 months. In pregnancy this is the result that leads to maternal-fetal medicine referral, ultrasound surveillance and discussion of amniocentesis.
IgG avidity, high	Above about 60 percent (assay-specific)	Infection more than 3 to 4 months ago. Before 16 to 18 weeks of pregnancy, this excludes a primary infection around conception or in the first trimester, which is the period of greatest fetal risk.
Pattern: IgG negative, IgM positive	Possible very early infection or false-positive IgM	Repeat both tests in 2 to 3 weeks. Appearance of IgG confirms a primary infection; persistent IgG negativity means the IgM was non-specific.
Newborn testing for congenital CMV	CMV PCR or culture on saliva or urine within 21 days of birth: detected or not detected	After 21 days a positive result cannot distinguish congenital infection from infection acquired at birth or through breast milk. Antibody tests are not used in newborns because maternal IgG crosses the placenta.

Positive CMV IgG (and what a positive IgM adds)

A positive CMV IgG means you were infected with cytomegalovirus at some point, most likely years ago in childhood or early adulthood, and that you carry the virus in a dormant state like the majority of adults worldwide. For a healthy, non-pregnant person this has no practical consequence: it does not cause symptoms, does not need treatment, and in day-to-day life you are not considered contagious, although carriers shed small amounts of virus in saliva and urine intermittently. In pregnancy, a positive IgG with a negative IgM is reassuring. It means a primary infection, the kind that carries a 30 to 40 percent risk of passing to the baby, cannot happen; reactivation or reinfection with a different strain can still transmit CMV to the fetus, but at a far lower rate, around 1 to 2 percent, and usually with milder consequences.

A positive IgM alongside the positive IgG raises the possibility of a recent primary infection but does not establish it. IgM persists for 6 to 12 months or longer in a substantial minority of people after a genuine infection, reappears with reactivation, and gives false-positive results with Epstein-Barr virus infection, parvovirus, other acute infections and rheumatoid factor. The IgG avidity test is the next step: high avidity means the infection occurred more than 3 to 4 months ago, which in the first half of pregnancy places it before conception or very early; low avidity means it was recent. A low-avidity result in a pregnant person leads to referral to maternal-fetal medicine, detailed ultrasound every 2 to 4 weeks, and discussion of amniocentesis for CMV PCR at 21 weeks or later, at least 6 to 8 weeks after the estimated infection. Trials have shown that high-dose valacyclovir started soon after a first-trimester primary infection lowers the rate of fetal transmission, so prompt specialist assessment matters.

In transplant medicine a positive IgG has a different meaning. For an organ transplant, a seronegative recipient receiving an organ from a seropositive donor (D+/R−) has the highest risk of CMV disease, typically 50 percent or more without prevention; a seropositive recipient has an intermediate risk from reactivation; and D−/R− the lowest. Antiviral prophylaxis or PCR-guided pre-emptive treatment is chosen on these results. In people with advanced HIV (CD4 count under 50) or on heavy immunosuppression, a positive IgG indicates the potential for reactivation disease (retinitis, colitis, pneumonitis), which is diagnosed by PCR and tissue examination rather than by antibodies. In a healthy adult with a mono-like illness and a negative mono test, a newly positive IgM with low avidity or a seroconversion from IgG-negative to positive confirms CMV mononucleosis, which resolves on its own over 2 to 6 weeks.

Common causes

Past infection acquired in childhood
Most seropositive adults were infected before age 10 from other children's saliva and urine, from breast milk, or at birth. Seroprevalence rises steadily with age and is higher with lower household income, larger families, daycare attendance and in many countries outside North America and Western Europe.
Past infection acquired in adolescence or adulthood
Through kissing and sexual contact, which is why seroprevalence climbs through the teens and twenties, and through close contact with young children: parents of toddlers in daycare and childcare workers seroconvert at 8 to 20 percent a year, far above the 1 to 2 percent a year of other adults.
Recent primary infection (IgG and IgM positive, low avidity)
Often symptomless; otherwise a mononucleosis-like illness with prolonged fever, fatigue and mildly raised liver enzymes. In pregnancy this is the pattern that matters, with fetal transmission in about 30 to 40 percent of cases, highest when infection occurs late in pregnancy but most harmful when it occurs around conception and in the first trimester.
Reactivation or reinfection in a seropositive person
Dormant virus reactivates during illness, stress, pregnancy and especially immunosuppression, and reinfection with a different strain occurs; either can make IgM transiently positive with high avidity. Fetal transmission from these events is about 1 to 2 percent.
False-positive IgM
Cross-reacting antibodies during Epstein-Barr virus mononucleosis, parvovirus B19, hepatitis, HIV seroconversion or other acute infections; rheumatoid factor and other autoantibodies; and non-specific binding. The commonest explanation for a positive IgM in a well person with a positive IgG.
Persistent IgM after an old infection
In 10 to 30 percent of people IgM remains detectable for 9 to 12 months or longer after primary infection. High IgG avidity identifies these cases.
Passive antibody from blood products or the mother
Intravenous immunoglobulin and transfusions transfer donor IgG for weeks to months, and infants carry maternal IgG for 6 to 12 months, which is why antibody tests are not used to diagnose infection in newborns or shortly after IVIG.

Symptoms that can go with it

None in the great majority of people with a positive IgG; the infection was silent or long forgotten
With a recent primary infection: fever lasting 1 to 3 weeks, marked fatigue, muscle aches, mildly sore throat and swollen glands, sometimes a rash (CMV mononucleosis, often with a negative mono test)
Mild hepatitis with raised ALT and AST, occasionally mild jaundice, during a primary infection
In pregnancy: usually no symptoms at all, which is why a recent infection is often discovered only through testing
In transplant recipients and people with advanced HIV: fever, low white cells and platelets, bloody diarrhea, breathlessness and cough, or blurred vision and floaters (CMV retinitis, which threatens sight)
In a newborn with congenital CMV: small size, jaundice, a pinpoint purple rash, enlarged liver and spleen, small head, seizures, or a failed newborn hearing screen; about 90 percent of infected newborns look normal at birth
In children with congenital CMV: progressive or late-onset hearing loss through the preschool years, which is why hearing is followed even when the newborn screen was passed

Negative CMV IgG (seronegative)

A negative CMV IgG means you have no antibodies to cytomegalovirus and, assuming you are not in the first 1 to 3 weeks of a brand-new infection, have never been infected. About 40 to 50 percent of US adults of childbearing age are in this position. There is nothing wrong with being seronegative, but it does mean you are susceptible to a primary infection, and in two settings that matters: pregnancy and transplantation.

In pregnancy, a seronegative person who has a primary CMV infection has about a 30 to 40 percent chance of passing the virus to the fetus, and the earlier in pregnancy the infection, the greater the chance of hearing loss or neurodevelopmental harm in an infected baby. The risk of acquiring CMV during pregnancy is about 1 to 2 percent overall but considerably higher for mothers of toddlers in daycare and for childcare and healthcare workers, and the main route is contact with a young child's saliva and urine. Studies in seronegative pregnant women show that simple hygiene measures cut the rate of infection substantially, which is the most useful thing to know if your IgG is negative. Routine CMV screening in pregnancy is not currently recommended in the US, so a negative result usually arises from testing after exposure or symptoms, or in some practices at the first prenatal visit.

Before transplantation, a negative IgG in a recipient matched with a positive donor (D+/R−) marks the highest-risk group for CMV disease, and prolonged antiviral prophylaxis or close PCR monitoring is planned accordingly. Seronegative people who are pregnant, very premature infants, and transplant and chemotherapy patients are given leukocyte-reduced or CMV-seronegative blood products to avoid transfusion-transmitted infection. A negative IgG with a positive IgM is a special case: it is either the first days of a primary infection, in which case IgG will appear within 2 to 3 weeks on a repeat test, or, more often in someone who feels well, a non-specific IgM result.

Common causes

Never infected
About half of US adults under 50, more in higher-income households and smaller families, and more in people without close contact with young children.
Very early primary infection
IgG takes 1 to 3 weeks to become detectable, so in the first days of infection IgM may be positive while IgG is still negative. A repeat in 2 to 3 weeks showing IgG seroconversion confirms the diagnosis.
Immunosuppression limiting antibody production
Profound immunodeficiency, B-cell-depleting drugs such as rituximab, and some primary immunodeficiencies can leave a person seronegative despite infection. In these patients CMV PCR, not serology, is used.
Loss of maternal antibody in infancy
Infants are IgG positive for 6 to 12 months from maternal antibody and then become negative unless they have acquired the virus themselves. A negative IgG in a child older than a year means no infection.
Assay differences near the cutoff
Low-level antibody from a distant infection can fall below the threshold of one assay and above another's. Discordant results between labs are repeated or resolved with a second method.

Symptoms that can go with it

None; seronegativity causes no symptoms
A new fever, fatigue and swollen glands lasting more than a week in a seronegative pregnant person should prompt repeat CMV IgG and IgM testing 2 to 3 weeks apart
In a seronegative transplant recipient, fever, falling blood counts, diarrhea or breathlessness in the months after transplant are checked with CMV PCR regardless of antibody results

Read it alongside

CMV IgM — the marker of possible recent infection; interpreted with IgG and avidity, never alone.
CMV IgG avidity — dates a primary infection to within or beyond the last 3 to 4 months; the key test when both IgG and IgM are positive in early pregnancy.
CMV PCR (viral load) on blood — detects active viral replication in transplant recipients and immunosuppressed people; serology is unreliable in them.
Mono spot and Epstein-Barr virus serology — a mono-like illness with a negative mono test is CMV in a substantial share of cases; EBV infection also causes false-positive CMV IgM.
Complete blood count — atypical lymphocytes, a mildly low platelet count or low white count accompany CMV mononucleosis; falling counts after transplant suggest CMV disease.
ALT and AST — mildly raised (2 to 5 times normal) in most primary infections; marked rises suggest another cause or severe disease.
Toxoplasma, rubella and parvovirus B19 serology — often drawn together in pregnancy when a fever, rash or fetal ultrasound finding needs an infectious cause identified.
Amniotic fluid CMV PCR and fetal ultrasound — the prenatal tests for fetal infection after a confirmed maternal primary infection; newborn saliva or urine PCR within 21 days confirms congenital infection.

What usually happens next

IgG positive and IgM negative, not pregnant: no action. In pregnancy this result means no primary infection; continue routine care, with standard hygiene around young children because reinfection, though much less risky, is possible.
IgG positive and IgM positive in pregnancy: ask for IgG avidity on the same sample. High avidity before 16 to 18 weeks is reassuring. Low or intermediate avidity leads to referral to maternal-fetal medicine, serial ultrasound, discussion of amniocentesis at 21 weeks or later and at least 6 to 8 weeks after the estimated infection, and a conversation about high-dose valacyclovir, which in a randomized trial reduced fetal transmission after first-trimester infection.
IgG negative and IgM positive: repeat both tests in 2 to 3 weeks. Seroconversion of IgG confirms a primary infection; persistent IgG negativity means the IgM was non-specific and no further testing is needed.
IgG negative in pregnancy: adopt the hygiene measures below, especially if you have a child under 3 in daycare or work with young children; some clinicians repeat the IgG each trimester in high-exposure situations.
A newborn whose mother had a confirmed or suspected infection in pregnancy, or who fails the newborn hearing screen, is small for dates, jaundiced or has a petechial rash: CMV PCR on saliva or urine within 21 days of birth. Infected babies have hearing checks, an eye examination, blood tests and a head ultrasound, and those with symptoms are considered for 6 months of oral valganciclovir, which improves hearing and developmental outcomes.
Transplant candidates and donors: IgG status is recorded for both, and D+/R− pairs receive antiviral prophylaxis (typically 3 to 6 months) or PCR-guided pre-emptive treatment after transplant; seronegative recipients receive leukocyte-reduced or seronegative blood products.

Diet, lifestyle and natural levers with evidence

What can move CMV antibodies once the cause is known. Nothing here replaces finding the cause.

Hygiene around young children's saliva and urine during pregnancy

Moderate evidence

No food, herb or supplement changes CMV antibodies or clears the virus, but behavior changes the chance of a primary infection in pregnancy. In an Italian prospective study of seronegative pregnant women with regular contact with young children, those given specific hygiene counseling seroconverted at 1.2 percent compared with 7.6 percent of those who were not counseled, and a French study found a halving of primary infections after counseling. The measures are not sharing food, utensils, cups, pacifiers or toothbrushes with young children, not kissing them on or near the mouth, washing hands for 15 to 20 seconds after diaper changes, wiping noses or handling toys, and cleaning surfaces that contact saliva or urine.

Leukocyte-reduced or CMV-seronegative blood products for people at risk

Strong evidence

Transfusion used to be a major route of CMV infection in seronegative pregnant women, very premature infants and transplant and chemotherapy patients. Removing white cells from donated blood by filtration, or using blood from seronegative donors, reduces transfusion-transmitted CMV to about 1 to 3 percent or lower in prospective studies, and the two approaches perform similarly. If you are seronegative and pregnant, or caring for a very premature baby or a transplant patient, confirming that transfused blood is leukocyte-reduced or seronegative is appropriate.

Handling of breast milk for very premature infants

Preliminary evidence

Seropositive mothers shed CMV in breast milk, and infants born before 30 weeks or under 1,500 g can develop symptomatic postnatal infection, though usually without the long-term harm of congenital infection. Freezing milk at −20°C for 72 hours reduces but does not eliminate transmission, and Holder pasteurization eliminates it at some cost to the milk's immune components. Because the benefits of mother's milk for premature infants are large, neonatal units weigh these options individually rather than advising against breastfeeding; full-term infants are not at meaningful risk.

Repeat and date the test rather than act on a single IgM

Strong evidence

What most often changes the meaning of a CMV result is not treatment but interpretation. A positive IgM alone has a positive predictive value for primary infection well under 50 percent in low-risk pregnant women; adding IgG avidity, and where needed a second sample 2 to 3 weeks later to look for a rising IgG or seroconversion, correctly reclassifies most of them. Testing during or just after an Epstein-Barr virus illness, with known rheumatoid factor, or within months of IVIG or transfusion makes false or borrowed results more likely, and this context should be on the request form.

When to see a clinician promptly

A pregnant person with a positive CMV IgM, a flu-like illness with prolonged fever, or a known exposure to a child with CMV: arrange IgG avidity or repeat testing promptly, since the window for interventions after a first-trimester infection is short.
Blurred vision, new floaters or loss of part of the visual field in anyone with advanced HIV (CD4 under 50) or on transplant-level immunosuppression: possible CMV retinitis, which can cause permanent sight loss within days and needs same-day ophthalmology assessment.
Fever, falling blood counts, bloody diarrhea, abdominal pain or breathlessness in the months after a transplant or during chemotherapy: CMV disease is diagnosed by PCR and treated urgently.
A newborn with jaundice, a pinpoint purple rash, a small head, poor feeding, seizures or a failed hearing screen: CMV testing must be done within 21 days of birth to count as congenital infection and to allow treatment to be considered.
A fever lasting more than 10 to 14 days with marked fatigue in an otherwise healthy adult, or a mono-like illness with a negative mono test, to identify the cause and exclude more serious conditions.
New or worsening hearing loss, speech delay or balance problems in a child known to have congenital CMV, since hearing loss can appear or progress through the preschool years.

Frequently asked questions

What does CMV IgG positive mean?

It means you were infected with cytomegalovirus at some point and carry the virus in a dormant form, like about half of US adults by age 40 and 90 percent of older adults. The infection was most likely silent or felt like a mild flu years ago. For a healthy person it needs no treatment and no follow-up. In pregnancy, a positive IgG with a negative IgM means a primary infection, the kind with the highest risk to the baby, cannot happen; in transplant medicine it determines the preventive strategy.

CMV IgG positive and IgM negative, do I need to worry?

No. This is the most common and most reassuring pattern. It means a past infection with no evidence of recent activity. If you are pregnant, you are not at risk of a primary CMV infection; reactivation or reinfection with a new strain can still rarely transmit the virus to the baby (about 1 in 100), which is why sensible hygiene around young children's saliva and urine is still advised, but no further testing is needed on the basis of this result.

What does a positive CMV IgM in pregnancy mean?

It raises the question of a recent infection but does not answer it: in low-risk pregnant women fewer than half of positive IgM results turn out to be primary infections, because IgM can persist for a year or more after an old infection, reappear with reactivation, and cross-react with Epstein-Barr virus and other infections. The next step is IgG avidity on the same sample. High avidity before 16 to 18 weeks means the infection was more than 3 to 4 months ago and the pregnancy is not at risk from a primary infection; low avidity means a recent infection and leads to referral to a maternal-fetal medicine specialist.

What is CMV avidity and what do high and low mean?

Avidity is how tightly your IgG antibodies bind the virus. Newly made antibodies bind loosely, and over 3 to 4 months the immune system refines them so they bind tightly. A low avidity (below about 30 to 40 percent, depending on the assay) means the infection began within roughly the past 3 to 4 months; a high avidity (above about 60 percent) means it is older than that; intermediate values are indeterminate and are repeated. In pregnancy a high avidity before 16 to 18 weeks is strong reassurance because it excludes an infection around conception or in the first trimester.

Can CMV IgM be a false positive?

Yes, frequently. CMV IgM assays cross-react with antibodies produced during Epstein-Barr virus mononucleosis, parvovirus, hepatitis and other acute infections; rheumatoid factor and other autoantibodies trigger them; and genuine IgM from an infection months or years ago persists in up to a third of people. That is why a positive IgM is never acted on alone: IgG avidity, a repeat sample 2 to 3 weeks later, and the clinical context decide whether it means anything.

Is a positive CMV IgG good or bad for pregnancy?

On balance it is good. A positive IgG (with negative IgM or high avidity) means you had CMV before pregnancy, so you cannot have the primary infection that transmits to the baby in 30 to 40 percent of cases. Reactivation and reinfection can still transmit, but at about 1 to 2 percent and generally with milder effects, and in countries where nearly all women are seropositive most congenital CMV arises this way simply because there are so many more seropositive mothers. A negative IgG is not bad either; it means you are susceptible and that hygiene around young children is worth taking seriously.

Is CMV IgG positive contagious?

Not in the way an active infection is. People with a past infection shed small amounts of virus in saliva, urine and genital secretions from time to time, especially young children, who can shed for months after a first infection. This is why toddlers are the main source of infection for pregnant women and why the hygiene advice centers on them. Healthy seropositive adults are not restricted in work, school, kissing partners or caring for others, and a positive IgG does not exclude you from most activities, although it is recorded for blood and organ donation.

How is congenital CMV diagnosed in a newborn?

By detecting the virus itself, with a PCR (or culture) on the baby's saliva or urine within the first 21 days of life. After 21 days a positive result could reflect infection picked up during birth or from breast milk, which does not carry the same risks. Antibody tests are not used because the baby's IgG is the mother's, and IgM is unreliable in newborns. Babies who test positive have hearing tests, an eye examination, blood counts, liver tests and a head ultrasound, and those with symptoms may be treated with 6 months of oral valganciclovir; all have hearing followed through early childhood.

References

Cytomegalovirus (CMV) tests. MedlinePlus, US National Library of Medicine (2023)View source
Clinical overview of congenital cytomegalovirus. Centers for Disease Control and Prevention (2024)View source
Bate SL, Dollard SC, Cannon MJ. Cytomegalovirus seroprevalence in the United States: the National Health and Nutrition Examination Surveys, 1988–2004. Clinical Infectious Diseases (2010)
Kenneson A, Cannon MJ. Review and meta-analysis of the epidemiology of congenital cytomegalovirus (CMV) infection. Reviews in Medical Virology (2007)
Revello MG, Tibaldi C, Masuelli G, et al.. Prevention of primary cytomegalovirus infection in pregnancy. EBioMedicine (2015)
Vauloup-Fellous C, Picone O, Cordier AG, et al.. Does hygiene counseling have an impact on the rate of CMV primary infection during pregnancy? Results of a 3-year prospective study in a French hospital. Journal of Clinical Virology (2009)
Prince HE, Lapé-Nixon M. Role of cytomegalovirus (CMV) IgG avidity testing in diagnosing primary CMV infection during pregnancy. Clinical and Vaccine Immunology (2014)
Shahar-Nissan K, Pardo J, Peled O, et al.. Valaciclovir to prevent vertical transmission of cytomegalovirus after maternal primary infection during pregnancy: a randomised, double-blind, placebo-controlled trial. The Lancet (2020)
Society for Maternal-Fetal Medicine, Hughes BL, Gyamfi-Bannerman C. Diagnosis and antenatal management of congenital cytomegalovirus infection: SMFM Consult Series No. 39. American Journal of Obstetrics and Gynecology (2016)
Kotton CN, Kumar D, Caliendo AM, et al.. The Third International Consensus Guidelines on the management of cytomegalovirus in solid-organ transplantation. Transplantation (2018)
Kimberlin DW, Jester PM, Sánchez PJ, et al.. Valganciclovir for symptomatic congenital cytomegalovirus disease. New England Journal of Medicine (2015)
Cytomegalovirus (CMV) infection. Mayo Clinic (2024)View source
Cytomegalovirus (CMV) infection. Merck Manual Professional Version (2024)

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