Congenital cytomegalovirus infection

Most common congenital viral infection worldwide.

Maternal infection types

Type	Risk to fetus
Primary infection	Highest risk
Reinfection	Lower risk
Reactivation	Lowest risk

Transmission risk by gestational age

Trimester of maternal infection	Fetal transmission risk	Severity risk
1st trimester	~30–40%	Most severe
2nd trimester	~40–50%	Moderate
3rd trimester	~60–70%	Usually mild

Timing of embryopathy vs fetopathy

Infection at 6–12 weeks - This is the highest-risk period.

Major effects:

• Neuronal migration defects
• Cortical malformations
• Microcephaly

Infection at 12–20 weeks

• Ventriculomegaly
• Intracranial calcifications
• White matter injury

Infection after 20–24 weeks

• Milder CNS involvement
• Hepatosplenomegaly
• Growth restriction

Fetal pathophysiology

CMV primarily affects: developing brain

Mechanisms:

• Neuronal destruction
• Impaired migration
• Calcification
• Gliosis

Also affects:

• Liver
• Bone marrow
• Placenta

Ultrasound timeline after infection

0–2 weeks after fetal infection - No ultrasound findings

3–6 weeks after infection

Early signs:

• Echogenic bowel
• Mild ventriculomegaly
• Hepatomegaly

6–10 weeks after infection

Progressive findings:

• Intracranial calcifications
• Ventriculomegaly
• Microcephaly emerging

>10 weeks

Late-stage features:

• Cortical malformations
• Severe brain injury
• Growth restriction

Major long-term complications

Especially neurological.

• Hearing loss (most common)
• Developmental delay
• Cerebral palsy
• Epilepsy

Prognostic ultrasound features

Poor prognosis indicators

• Microcephaly
• Ventriculomegaly
• Cortical malformations
• Cerebellar hypoplasia
• Hydrops

Placental involvement

CMV affects placenta significantly.

Findings:

• Thick placenta
• Calcifications
• Inflammation

Placental dysfunction contributes to: fetal growth restriction.

Diagnosis — maternal and fetal

Maternal testing

• CMV IgM
• CMV IgG
• IgG avidity

Avidity interpretation

Avidity	Meaning
Low	Recent infection
High	Old infection

Fetal diagnosis

Most definitive: Amniotic fluid PCR

• Timing:
• ≥21 weeks
• ≥6–8 weeks after maternal infection

CMV classic cluster

• Ventriculomegaly
• Intracranial calcifications
• Echogenic bowel
• Hepatosplenomegaly

This combination is very characteristic.

Congenital CMV severity is determined mainly by gestational age at infection, with early infection causing severe neuronal migration defects and later infection producing milder systemic findings, and ultrasound abnormalities typically appearing 3–10 weeks after fetal infection.