Comparative nanostructure consideration on novel coronavirus and possibility of transplacental transmission

To the Editors:

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection or novel coronavirus infection is a new emerging viral infection that leads to coronavirus disease 2019 (COVID-19). A large outbreak of SARS-CoV-2 infection occurred in early 2020. From its first appearance, the virus spread to many countries worldwide.¹ SARS-CoV-2 infection leads to respiratory disorders (COVID-19). In addition, airborne transmission of the virus from human to human is confirmed. In gynecology, the effect of COVID-19 during pregnancy needs further studies. As noted by Rasmussen et al,² there are many issues obstetricians need to know. Of several issues, finding infection in neonates born to mothers with SARS-CoV-2 infection draws the attention of the medical society toward a possible transplacental mode of transmission.

In fact, many viruses can cross the placenta and cause infection from the mother to the neonate. Good examples of viruses that cross the placenta are the human immunodeficiency virus (HIV) and hepatitis virus.2, 3, 4 Based on the nanomedicine concept, the transplacental transmission of HIV is explained by the particle size of the virus and the pore size of the placenta.² Conceptually, the viral pathogen that is smaller than the pore size of the placenta can pass the placenta and further cause neonatal infection. Applying nanostructure size analysis on the novel coronavirus, the estimated size of the virus is about 50 to 120 nm. The size of the virus is larger than the pore size of the placenta (about 10 nm). Therefore, it is unlikely that transplacental transmission of novel coronavirus can occur if there is no placental pathology. Indeed, the observations from China also show no case of vertical transmission.⁵ The cause of SARS-CoV-2 infection in neonates could possibly be due to respiratory transmission from close contact with the mother.