Mother-to-child transmission of severe acute respiratory syndrome coronavirus 2: review of classification systems and systematic reviews.

Abstract

To review the various classification systems for mother-to-child transmission (MTCT) of SARS-CoV-2 and collate existing evidence on systematic reviews of MTCT of SARS-CoV-2. To-date, there are three classification systems for MTCT of SARS-CoV-2, including the WHO classification developed by expert consensus, based on in-utero, intrapartum and postnatal exposure of the babies to the virus. The systems variously classify babies tested for suspected SARS-CoV-2 infection as confirmed, probable, possible, indeterminate and unlikely for MTCT. To-date, 68 systematic reviews have been published between December 2019 and March 2021 on SARS-CoV-2 MTCT. Most of the reviews included cases series and case reports in their pooling of data, and often used SARS-CoV-2 infection and test positivity interchangeably. Several classification systems are available to assist in determining the timing of SARS-CoV-2 infection in new-borns. Existing reviews of MTCT are of poor quality and report variable rates of SARS-CoV-2 positivity. A high-quality systematic review is needed on the extent of confirmed vertical transmission of SARS-CoV-2, risk factors for MTCT of SARS-CoV-2, the prevalence and persistence of viral particles or immunological response in reported biological samples. Primary studies should categorize MTCT using classifications, such as WHO classification system that considers the strength of the timing of classification and persistence of positivity, taking into account the sterility of the collected samples.