Serial Head and Brain Imaging of 17 Fetuses With Confirmed Zika Virus Infection in Colombia, South America.

OBJECTIVE: To evaluate fetal ultrasound and magnetic resonance imaging findings among a series of pregnant women with confirmed Zika virus infection to evaluate the signs of congenital Zika syndrome with respect to timing of infection.
METHODS: We conducted a retrospective case series of pregnant women referred to two perinatal clinics in Barranquilla and Ibagué, Colombia, who had findings consistent with congenital Zika syndrome and Zika virus infection confirmed in maternal, fetal, or neonatal samples. Serial ultrasound measurements, fetal magnetic resonance imaging results, laboratory results, and perinatal outcomes were evaluated.
RESULTS: We describe 17 cases of confirmed prenatal maternal Zika virus infection with adverse fetal outcomes. Among the 14 symptomatic women, the median gestational age for maternal Zika virus symptoms was 10 weeks (range 7-14 weeks of gestation). The median time between Zika virus symptom onset and microcephaly (head circumference less than 3 standard deviations below the mean) was 18 weeks (range 15-24 weeks). The earliest fetal head circumference measurement consistent with microcephaly diagnosis was at 24 weeks of gestation. The earliest sign of congenital Zika syndrome was talipes equinovarus, which in two patients was noted first at 19 weeks of gestation. Common findings on fetal magnetic resonance imaging were microcephaly, ventriculomegaly, polymicrogyria, and calcifications.
CONCLUSION: Our analysis suggests a period of at least 15 weeks between maternal Zika virus infection in pregnancy and development of microcephaly and highlights the importance of serial and detailed neuroimaging.