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.