Cytomegalovirus pada Kehamilan

01Pathophysiology

CMV is a ubiquitous herpesvirus that establishes lifelong latency after primary infection. When a seronegative pregnant woman acquires CMV for the first time (primary infection), the transmission rate to the fetus is approximately 30-40%, and the risk of severe fetal disease is highest during the first trimester. Reactivation or reinfection with a different CMV strain can also cause congenital infection, but the disease severity is generally milder because pre-existing maternal antibodies offer partial protection.

Once the virus crosses the placenta, it has a strong tropism for rapidly dividing progenitor cells, particularly in the developing brain, inner ear, liver, and hematopoietic system. In the CNS, CMV targets the germinal matrix zone lining the ventricles, which is the proliferative zone for neuronal and glial precursors. This is exactly why the calcifications are periventricular in distribution, a hallmark finding that distinguishes congenital CMV from congenital toxoplasmosis (which produces diffuse, scattered intracranial calcifications). Destruction of these progenitor cells leads to migration abnormalities, lissencephaly, polymicrogyria, and ultimately microcephaly from impaired brain growth.

In the inner ear, CMV infects the stria vascularis and spiral ganglion neurons of the cochlea, producing sensorineural hearing loss (SNHL). This is the single most common sequela of congenital CMV and the leading nongenetic cause of SNHL in children. Critically, hearing loss may be progressive or late-onset, meaning a neonate can pass the initial hearing screen and still develop hearing impairment months to years later.

Hepatic involvement reflects viral replication in hepatocytes and biliary epithelium, causing a conjugated (direct) hyperbilirubinemia and elevated transaminases. The petechial rash and "blueberry muffin" spots result from dermal extramedullary hematopoiesis, a compensatory response to bone marrow suppression. Thrombocytopenia is common and results from both direct marrow infection and peripheral destruction.

Chorioretinitis occurs because CMV infects retinal pigment epithelium and neurosensory retina, producing white, necrotizing lesions that may threaten vision if the macula is involved.

02Classification and Clinical Manifestation

A critical testing point: the distinction between symptomatic and asymptomatic is not merely academic. Only symptomatic neonates with CNS involvement currently meet the treatment threshold for antiviral therapy. However, all confirmed congenital CMV cases, regardless of symptom status, require long-term audiologic follow-up because hearing loss can emerge or worsen over time.

03Diagnostic Workup

The diagnostic cornerstone is CMV PCR from urine or saliva collected before 21 days of life. This cutoff is essential because CMV can be acquired postnatally (through breast milk or contact), and a positive PCR after 21 days cannot reliably distinguish congenital from postnatal infection. If a child older than 21 days is suspected of having congenital CMV, the next step is to check the dried blood spot (Guthrie card) from the newborn metabolic screen using retrospective PCR testing, though sensitivity is lower.

Saliva PCR is highly sensitive but can yield false positives in breastfed infants due to CMV shed in breast milk. Therefore, a positive saliva PCR should be confirmed with a urine specimen before establishing the diagnosis.

Once congenital CMV is confirmed, neuroimaging is performed to determine whether CNS disease is present, as this drives the treatment decision. Head ultrasound is a reasonable first-line imaging modality, but MRI is superior for detecting cortical migration abnormalities and white matter lesions that ultrasound may miss.

Maternal serology (CMV IgM and IgG with avidity testing) can help determine whether the mother had a primary infection during pregnancy. Low IgG avidity indicates recent primary infection (within the past 3-4 months), while high avidity suggests remote infection or reactivation. However, maternal serology is a supporting tool; it does not confirm or exclude congenital infection in the neonate.

04Management and Treatment

Valganciclovir is the oral prodrug of ganciclovir and is the preferred antiviral because it can be given enterally. Intravenous ganciclovir (6 mg/kg/dose IV every 12 hours) is reserved for neonates who cannot tolerate oral medication. The landmark trial demonstrating benefit showed that 6 months of valganciclovir improved hearing outcomes at 12 and 24 months and modestly improved neurodevelopmental scores compared to 6 weeks of treatment.

The primary dose-limiting toxicity is neutropenia, which occurs in up to 20% of treated infants. Neutrophil counts must be monitored weekly for the first 6 weeks. If the absolute neutrophil count drops below 500/mm${}^3^3$, the drug should be held and restarted at the same dose once counts recover. Thrombocytopenia and hepatotoxicity are less common but also warrant surveillance.

Treatment should be initiated within the first month of life for optimal outcomes. Starting therapy beyond 1 month of age is associated with diminishing benefit, and antiviral treatment is generally not recommended if initiated after the neonatal period for congenital infection.

For long-term management, all children with confirmed congenital CMV need serial audiologic and developmental assessments regardless of initial symptom status. Hearing aids or cochlear implantation may be necessary for children with progressive bilateral SNHL. Ophthalmologic follow-up is indicated for those with chorioretinitis.

There is currently no licensed CMV vaccine, though several candidates are in clinical trials. Behavioral prevention for seronegative pregnant women includes hand hygiene after contact with young children's saliva and urine, which are the primary routes of horizontal CMV acquisition.

05Differential Diagnosis and Distractors

06Traps and High-Yield Pearls

The single most tested concept in congenital CMV is the 21-day diagnostic window. A vignette will describe a 2-month-old with sensorineural hearing loss and periventricular calcifications, then ask for the next step. Students who pick "urine CMV PCR" at that age are falling into the trap, because a positive result after 21 days cannot confirm congenital (versus postnatal) infection. The correct answer in that scenario is to retrieve the newborn dried blood spot (Guthrie card) for retrospective CMV PCR.

Another common pitfall involves confusing periventricular calcifications (CMV) with diffuse or basal ganglia calcifications (toxoplasmosis). When a vignette describes intracranial calcifications in a neonate, the location of the calcifications is the discriminator, not their mere presence.

Students also frequently miss that congenital CMV is the most common congenital infection overall and the leading nongenetic cause of sensorineural hearing loss in children. A vignette describing a child who fails a newborn hearing screen with no other risk factors should prompt consideration of congenital CMV, even without the classic "blueberry muffin" rash or hepatosplenomegaly.

The treatment trap involves prescribing antivirals to asymptomatic infants. Valganciclovir carries real toxicity (neutropenia), and current guidelines reserve treatment for symptomatic infants with CNS involvement. The exam tests whether you recognize that the benefit-risk calculus differs between symptomatic CNS disease and asymptomatic infection.

Finally, remember that hearing loss in congenital CMV can be delayed and progressive. A normal ABR at birth does not rule out future hearing impairment. This is why long-term audiologic surveillance is recommended for all confirmed cases, and it is the reason congenital CMV screening programs are gaining traction even for asymptomatic neonates.