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Vertical transmission of coronavirus across placenta

Date: 19 July 2020 Tags: Miscellaneous

Issue

 A study has found evidence that confirms vertical transmission of SARS-CoV-2 virus from the mother to the foetus. The route of infection is through the womb (in utero) well before the onset of labour and delivery of the baby.

 

Background

Transmission through droplets and contact with contaminated surfaces seem to be the major routes of novel coronavirus spread. The World Health Organization recently acknowledged the short-range aerosol transmission of the virus.

 

Details

  • Studies have already suggested vertical transmission as a possible route but have not been able to provide strong evidence about the route of spread — transplacental or transcervical of the virus from the mother to the child.

  • These studies could not confirm the transmission route because samples of the placenta, amniotic fluid and blood of the mother and the newborn were not collected and tested in every mother–infant pair.

  • During a study, the placenta and nasopharyngeal swab samples of the mother were tested for the virus. Though nasopharyngeal swab samples of the newborn collected on the day of birth and on two other days, plasma and stool samples tested positive for the virus.

  • Hence the researchers classified it a “probable” case of the congenital route of vertical transmission.

  • The research found that the virus first occurs in the mother’s blood and later causes placental infection and inflammation.

  • The virus then gets into the blood of the neonate following placental infection. The neonate also showed clinical manifestation of COVID-19 in terms of neurological signs and symptoms.

  • To check for vertical transmission, the researchers first collected clear amniotic fluid prior to rupture of membranes. The amniotic fluid tested positive for two genes of the virus. The baby was delivered through the caesarean section to avoid infection during normal childbirth.

  • The amount of virus in different tissues both in the mother and newborn varied. Viral load was much higher in placental tissue than in amniotic fluid and maternal or neonatal blood.

  • In the case of the newborn, the nasopharyngeal sample collected on day three after birth had a higher viral load, while the blood contained the least amount of the virus.