Clinical and experimental evidence for transplacental vertical transmission of flaviviruses

The Zika virus (ZIKV) epidemic outbreak in Americas in 2016 attracted global attention because of the association of the virus infection with severe birth defects such as microcephaly, mediated through transplacental virus transmission during pregnancy. Less well-known, but also reported is the increasing evidence that prenatal vertical transmission can be caused by other flaviviruses such as dengue virus (DENV). Currently, the mechanism(s) that cause the vertical transmission of flaviviruses is understudied. Here we review the published reports of clinical evidence of intrauterine transmission of ZIKV and other flaviviruses. We also discuss the animal models for flavivirus infection during pregnancy that have been developed to study the mechanisms underlying the transplacental transmission of flaviviruses in order to develop potential countermeasures for its prevention. •Clinical evidence of transplacental transmission of ZIKV, DENV and other flaviviruses is reviewed.•ZIKV transplacental transmission causes microcephaly and other congenital abnormalities.•Transplacental transmission from mother to fetus/infant also reported for DENV, JEV, WNV and YFV.•Animal models of flavivirus infection during pregnancy enables mechanistic study of transplacental transmission.