Abstract

Maternal infection with SARS-CoV-2 has led to concerns about the potential for mother-to-child transmission in pregnancy, with uncertainty about implications for the infant. We conducted a review of the evidence published from 2020 to 2021. We included 472 studies (206 cohort studies, 266 case series and case reports; 28952 mothers, 18237 babies). Overall, 2% of the 14271 babies born to mothers with SARS-CoV-2 infection tested positive for the virus. Of the 592 SARS-CoV-2 positive babies with data on the timing of exposure and type and timing of tests, 14 had confirmed mother-to-child transmission: seven in utero, two during labour, and five during the first days after birth. Severe maternal COVID-19 (including ICU admission and maternal death) was strongly associated with SARS-CoV-2 positivity in infants. SARS-CoV-2 positivity rates were found to be low in babies born to mothers with SARS-CoV-2 infection. Evidence suggested vertical transmission – where the virus passes from mother to baby during the period immediately before and after birth, e.g. across the placenta, in breast milk, or through direct contact during or after birth - of SARS-CoV-2 was possible, although this was rare. Severity of maternal COVID-19 disease also appeared to be associated with SARS-CoV-2 positivity in offspring.