A new insight into the definition of microcephaly in Zika congenital syndrome era

This study aimed to compare the anthropometric measurements and body proportionalities of neonates born before the Zika virus epidemic with those born during this period. We compared 958 neonates born during the pre-Zika epidemic with 264 neonates born during the epidemic period. The newborns had their head circumference, weight, and length classified according to the Fenton & Kim growth chart. We considered disproportionate those individuals that presented microcephaly and adequate weight or length for sex and gestational age, and those whose head circumferences were lower than the ratio ((length / 2) + 9.5) - 2.5cm. We estimated the frequencies of Zika positivity and brain imaging findings among neonates with microcephaly born during the epidemic period, concerning the anthropometric and body proportionality parameters. Low weight and proportionate microcephaly were similar among newborns from both periods. However, the frequencies of newborns with microcephaly with a very low length and disproportionate microcephaly were higher among the neonates of the epidemic period with brain abnormalities and positive for Zika virus. We conclude that, at birth, the disproportion between head circumference and length can be an indicator of the severity of microcephaly caused by congenital Zika.