Pharyngeal sampling for PCR-testing in the investigation of SARS-COV-2 vertical transmission in pregnancy

The novel COVID-19 global pandemic has raised, among many others, major concerns regarding the impact of infection during pregnancy. Current evidence suggests that vertical transmission from mother to baby, antenatally or intrapartum, does occur, but is uncommon. According to the published reports of infants born to COVID-19-affected mothers, as well as the anecdotal experience of current practices worldwide, it appears that investigations regarding the potential of SARS-COV-2 vertical transmission in pregnancy have so far been based, to a large extent, on PCR testing of neonatal pharyngeal swab samples. Given that the transplacental route of intrauterine transmission for SARS-COV-2 is less likely to immediately involve the upper respiratory tract of the newborn, contrary to what happens after birth, it would be advisable to include appropriate biological samples, such as cord blood, placenta, amniotic fluid and neonatal blood, along with the pharyngeal samples, in order to contribute significantly to such investigations. It is important to point out that negative PCR tests of neonatal pharyngeal samples do not exclude the possibility of intrauterine viral transmission, while positive pharyngeal swabs are more likely to reflect intrapartum or postpartum contaminants, rather than antenatal intrauterine transmission, in the absence of other criteria. Revision and enhancement of the so far prevailing practices appear important, in order to facilitate the development of good clinical practice for managing neonates and ensuring safety of families and healthcare providers.