An interesting article published in Obstetrics and Gynaecology by Naima and others April 26th 2021 researched this important subject to characterise maternal immune response after SARS-CoV-2 infection during pregnancy and to quantify the efficiency of trans-placental antibody transfer. 

The researchers conducted a prospective cohort study of pregnant patients who had tested positive for SARS-CoV-2 infection at any point during pregnancy and collected paired maternal and cord blood samples at the time of delivery.  

They used Elisa and neutralisation assays to measure maternal plasma and cord blood concentrations and neutralising potency of immunoglobulin IgG, IgA and IgM antibodies directed against the SARS-CoV-2 spike protein.  

They also reviewed differences in concentrations according to symptomatic compared with asymptomatic infections and time from positive PCR test result to delivery and analysed these using non-parametric tests of significance.  

The ratio of cord to maternal anti-receptor binding domain IgG titres was analysed to assess trans-placental transfer efficiency.  

32 paired samples were analysed and detectable anti-receptor binding domain IgG was detected in 100% of maternal and 91% of cord blood samples.  

Functioning neutralising antibody was present in 94% of the maternal and 25% of cord blood samples.  

Symptomatic infection was associated with a significant difference in median maternal anti-receptor binding domain IgG titres compared with asymptomatic infection. 

Median maternal anti-receptor binding domain IgG titres were not significantly higher in patients that delivered more than 14 days after a positive PCR test result compared with those who delivered within 14 days.  

They concluded that their results demonstrated a robust maternal neutralising and anti-receptor binding domain IgG response after SARS-CoV-2 infection.  

However, there was a lower than expected efficiency of trans-placental antibody transfer and a significant reduction in neutralisation between maternal blood and cord blood.  

Maternal infection did confer some degree of neo-natal antibody protection, but the robustness and durability of protection requires further study they suggest.  

They went on to argue that although their data demonstrated that pregnant women were capable of consistently mounting a robust anti-receptor binding domain IgG and neutralising response to SARS-CoV-2 infection, even if they were symptomatic at the time of diagnosis, they felt that this response was durable and provided some support that vaccination in this population would be effective.  

However, they felt the trans-placental antibody transfer was inefficient at only 81% after infection.  

An interesting study, which shows that more research is required to understand the nature of SARS-CoV-2 infection during pregnancy and within the neonate.  

The London General Practice as a leading London doctors’ clinic is delighted to offer PCR swab testing and COVID antibody testing with same day results.  

The London General Practice has a highly specific antibody test which correlates with neutralising antibodies and provides reassuring evidence of antibody production post vaccination.

Dr Paul Ettlinger

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