*2.2. Patient Selection and Specimens*

Placental tissues were obtained from 4 ZIKV-infected women and 4 control women. In the control women, the absence of ZIKV, Chikungunya virus (CHIKV), and DENV was confirmed by RT-PCR, done in placental tissue at the Central Epidemiological Laboratory of the Mexican Institute of Social Security (IMSS). For the 4 ZIKV-infected women, the RT-PCR diagnosis of ZIKV was made during the acute phase of ZIKV infection. In the newborns of the 4 ZIKV-infected women, detection of ZIKV was confirmed by RT-PCR on neonatal serum, amniotic fluid, and umbilical cord by the Mexican Institute of Diagnosis and Epidemiological Reference (InDRE), and the absence of CHIKV, DENV, and West Nile virus in these samples was confirmed by RT-PCR done by the National Institute of Respiratory Diseases (INER).

The pregnancies of ZIKV-infected women enrolled in this study were closely followed at INPer in Mexico City. A multidisciplinary clinical team, including maternal-fetal clinicians, geneticists, and pediatric neurologists, assessed the ultrasonographic diagnoses of described fetal alterations; prenatal findings were confirmed at birth. Immediately after giving birth by cesarean section, placental samples were fixed and processed as described below.
