Adverse pregnancy outcomes according to gestational age of
ZIKV maternal infection
Of the 92 women with ZIKV infection in the first trimester, 35.9% had
an adverse pregnancy outcome versus 2.8% and 1.9% in the second and
third trimesters, respectively (Table 2). Most (76.7%) of adverse
pregnancy outcomes potentially related to ZIKV occurred when the
infection was acquired during the first trimester.
Importantly, only one of the seven infants whose mothers had ZIKV
infection beyond the first trimester (14 weeks) was classified as
typical CZS phenotype. Three of the remaining infants were intrauterine
growth restricted what could be related to the moderate microcephaly in
whom no brain abnormalities were detected. Two had been congenitally
infected with CMV, probably explaining their brain imaging findings, and
one had clinical and imaging findings of a possible inborn error of
metabolism. None of these infants had positive ZIKV results. These 5
infants with other plausible causes for the observed postnatal CNS
anomalies were excluded from the typical CZS phenotype classification.
The gestational age of ZIKV infection that best predicted adverse
outcomes was 11 completed weeks of pregnancy (Figure 2). The relative
risk of adverse pregnancy outcomes potentially related to ZIKV infection
was 14.0[95%CI:7.6-26.0] for maternal infection acquired< 11 weeks as compared to more advanced gestational
ages. Gestational age less than eleven completed weeks (11.9) was also
the best predictor of the typical CZS phenotype with brain
abnormalities. These were much more likely to occur with maternal
infection < 11 weeks of gestation than afterward
(relative risk=76.2[95%CI:10.1-576.6]).