SARS-CoV-2, WHO definition and categorization of the timing of mother-to-child transmission.

This scientific brief was prepared based on results of evidence synthesis and a WHO expert consultation. The WHO COVID-19 LENS (Living Evidence Synthesis) working group consolidated available evidence, based on rapid reviews of the literature and results of a living systematic review on pregnancy and COVID-19 (up to October 7, 2020), on potential mechanisms of vertical transmission of infectious pathogens, feasibility of vertical transmission of SARS-CoV-2, data related to interpretation of positive SARS-CoV-2 virologic and serologic neonatal tests, lessons from diagnosis of other congenital infections, and existing proposed definitions to classify timing of vertical transmission of SARS-CoV-2.