Pregnant women with COVID-19 do not infect their foetus – but also do not pass on very many antibodies, researchers have found.
It is already known that pregnant women are at a raised risk of severe COVID-19. Dr Andrea Edlow of Harvard Medical School, Boston, USA, and colleagues measured the impact on the foetus of maternal infection.
They tested 127 pregnant women for viral load and antibody transmission through the placenta. All were in their third trimester.
Of the women 64, tested positive for COVID-19. Tests found no COVID-19 virus in their own blood, umbilical cord blood or in placentas, and there was no evidence of viral transmission during birth.
Although most of the women developed antibody responses against COVID-19, transfer of anti-COVID-19 antibodies through the placenta was significantly lower than transfer of anti-influenza antibodies, the researchers say.
The study appeared in JAMA Network Open yesterday (22 December).
Dr Edlow said: "Our finding of compromised mother-to-baby transfer of SARS-CoV-2-specific antibodies in third trimester infections has implications for maternal vaccine administration. Specifically, it highlights that pregnant women are a key population to consider in vaccine rollouts. It also raises questions regarding the optimal timing of vaccine administration to best support maternal and newborn immunity.
"Understanding the mechanisms underlying this inefficient transfer of SARS-CoV-2-specific antibodies after third trimester infection, as well as understanding whether vaccine-generated antibodies have the same or different properties than those from actual infection with the virus, will be critical directions for future research," she added.
Edlow, A. G. et al. Assessing maternal, neonatal SARS-CoV-2 viral load, transplacental antibody transfer, placental pathology. JAMA Network Open 22 December 2020; doi: 10.1001/jamanetworkopen.2020.30455
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