How should a pregnant woman with possible primary cytomegalovirus exposure be evaluated and managed?

Evaluation and Management of Pregnant Women with Possible Primary CMV Exposure

Initial Serologic Evaluation

Draw CMV IgG and IgM antibodies immediately, with IgG avidity testing if both are positive, to establish whether primary infection has occurred. 1

The diagnostic approach depends on serologic patterns:

• IgM positive + IgG positive with low avidity OR documented IgG seroconversion confirms primary maternal CMV infection 1
• IgM negative + IgG negative rules out CMV infection entirely 2
• IgG positive alone with high avidity indicates prior infection, not acute 1
• Significant rise in IgG titer with or without IgM and high avidity suggests secondary (reactivation) infection 1

Counseling After Confirmed Primary Infection

Inform parents that primary maternal CMV infection carries a 30-40% risk of vertical transmission to the fetus and a 20-25% risk of long-term sequelae if the fetus becomes infected 1. The risk of transmission increases with advancing gestational age, but the severity of fetal effects is significantly worse when infection occurs during the first half of pregnancy 3, 4.

Amniocentesis for Fetal Diagnosis

If primary maternal infection is confirmed or strongly suspected, recommend amniocentesis with CMV PCR to diagnose fetal infection. 2, 1

Critical timing requirements:

• Perform at least 7 weeks after presumed maternal infection (allows time for viral replication in fetal kidneys and secretion into amniotic fluid) 1
• Perform after 21 weeks of gestation for optimal sensitivity 2, 1
• CMV DNA PCR on amniotic fluid is the best diagnostic test 2

Quantitative CMV DNA levels in amniotic fluid may help predict fetal outcome, though this remains an adjunctive tool 1.

Serial Ultrasound Monitoring

Following diagnosis of fetal CMV infection, perform serial ultrasound examinations every 2-4 weeks to detect sonographic abnormalities 1. Look specifically for:

• Intracranial calcifications
• Ventriculomegaly or microcephaly
• Echogenic bowel 2
• Hepatosplenomegaly
• Hydrops fetalis
• Intrauterine growth restriction 2
• Ascites 2

Critical caveat: Normal ultrasound findings do NOT guarantee a normal outcome. 1 Even with normal prenatal imaging, 7-15% of infected fetuses may develop late-onset sequelae, particularly sensorineural hearing loss 4, 5. Prenatal imaging failed to predict childhood adverse outcomes in second and third trimester infections 4.

Management of Secondary (Reactivation) Infection

For secondary maternal infection (significant IgG rise with high avidity), amniocentesis may be considered, but the risk-benefit ratio differs substantially because vertical transmission rates are much lower than with primary infection 1. The decision requires careful discussion of the lower transmission risk versus procedural risks.

Antiviral Treatment Considerations

Currently, antiviral treatment during pregnancy is not routinely recommended for maternal or fetal CMV infection in immunocompetent women 2, 3. However:

• Valganciclovir is recognized as the treatment of choice during pregnancy if treatment is pursued, though experience in human pregnancy is limited 2
• Consider local therapy (intraocular implants or intravitreous injections) in the first trimester if maternal CMV retinitis is present, to limit fetal exposure 2
• Systemic antiviral therapy may be started after the first trimester if needed for maternal disease 2

Neonatal Planning

Inform pediatric providers at delivery about:

• The antenatal diagnosis of maternal CMV infection
• Any prenatal workup performed
• Any abnormal ultrasound findings 2

This ensures appropriate neonatal evaluation, including CMV PCR from urine or saliva within the first 3 weeks of life to confirm congenital infection 6, 3.

Screening Recommendations

Routine universal screening of all pregnant women for CMV is NOT currently recommended 1, 5. However, serologic testing should be considered for:

• Women with influenza-like illness during pregnancy 1
• Detection of sonographic findings suggestive of CMV (echogenic bowel, intracranial calcifications, etc.) 2, 1
• Seronegative healthcare or childcare workers (may offer serologic monitoring) 1
• Seronegative women with young children in daycare (monitoring may be considered) 1

Prevention Education

Emphasize behavioral hygiene measures to prevent CMV acquisition, particularly for seronegative pregnant women with young children or those working in childcare settings 7, 5. These include handwashing after diaper changes, avoiding sharing utensils/cups with young children, and avoiding contact with saliva from young children.