ABSTRACT
We conducted a systematic review according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines (CRD42020183500). We searched PubMed, Medline, Embase and China National Knowledge Infrastructure using search terms neonate, pregnancy, COVID-19, 2019-nCoV, SARS-CoV-2 and similar variants until 23 May 2020. Studies reporting mothers who tested positive for SARS-CoV-2 by reverse transcriptase PCR (RT-PCR) and whose newborns were tested by RT-PCR were included. Seventeen studies (two studies in Chinese language) were included, with mean quality assessment score of 5.29 based on the Newcastle-Ottawa Scale. Four hundred and two COVID-19-positive mothers delivered 405 newborns, of which 330 newborns underwent early RT-PCR tests. Nine of 330 newborns tested positive for SARS-CoV-2. The average pooled incidence of vertical transmission was 16 per 1000 newborns. Therefore, current evidence shows that the risk of vertical transmission of SARS-CoV-2 is low. One of the nine newborns had elevated IgM antibodies and was symptomatic at birth which suggested intrauterine infection. This is supported by reports of SARS-CoV-2 in amniotic fluid and fetal side of the placenta. On the placenta, the expression of ACE2 acts as the receptor for cell entry of SARS-CoV-2. Additionally, vertical transmission can occur during vaginal delivery through contact with virus present in mother's stool.