Table 1.
Indicators for diagnosis of ZIKV infection in the first trimester.
| Diagnosis | Exam Timing | Morphological Features | Further Remarks |
|---|---|---|---|
| ZIKV infection | Polymerase Chain Reaction analysis of amniotic fluid best period to perform an amniocentesis is between the 21st and 22nd week | Around 6–9 weeks are required after maternal infection for the virus to be eliminated in the fetal urine in amounts detectable in the amniotic fluid | |
| Anti-CMV IgM antibodies Virus-specific IgM antibodies may be detectable >3 days after onset of illness |
Blood exam | No detectable virus-specific IgM antibodies in serum collected within 7 days of illness onset | IgM testing should be repeated on a convalescent-phase sample to rule out infection in the mother with a clinical syndrome suggestive of ZIKV infection. IgM antibodies are only present in 70% infected babies |
| Microcephaly | Neurosonographic approaches for the detection of malformations | Head circumference < 2SDS | An estimated 1% to 13% risk of microcephaly is associated with maternal infection in the first trimester of pregnancy |
| Ventriculomegaly | Ultrasound examination | Atrial diameter ≥ 10 mm on prenatal ultrasound | Roughly 5% of cases of mild to moderate ventriculomegaly reportedly arise from congenital fetal infections, such as CMV, toxoplasmosis and ZIKV |
| Brain calcifications Posterior fossa destruction lesions | Ultrasound examination; MRI | More visible in II-III trimester | Punctate calcifications between the cortex and subcortical white matter |
| Disproportion in fetal growth | Ultrasound | Femur-sparing profile of growth restriction | Infection in the first trimester is linked to the highest risk of structural and developmental anomalies |
| Germinolytic cysts (GLC) and lenticulostriate vasculopathy (LSV) | Transvaginal scan | Found in up to 37% of newborns exposed to ZIKV in utero, might constitute potential risk factors for worse early neurodevelopmental outcomes | |
| Cerebellar hypoplasia and migrational disorders such as polymicrogyria (PMG) | MRI | Polymicrogyria and pachygyria mostly detected in the frontal lobes |