Definition and categorization of the timing of mother-to-child transmission of SARS-CoV-2
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. WHO convened a multidisciplinary, international panel of experts between October and November 2020 to review the evidence and propose a consensus initial classification system for the timing of vertical transmission of SARS-CoV-2. The panel included experts in obstetrics, neonatology, paediatrics, epidemiology, virology, infectious disease, congenital infections, and placental pathology. The selection of the panel ensured geographic representation, gender balance, and no important conflicts of interest, in accordance with WHO standard procedures.