The safety of COVID-19 mRNA vaccination during pregnancy is still a topic of concern. The effects on placenta development have been poorly studied, even though correct placenta development is essential for healthy pregnancy outcomes. Here we investigated the effect of the maternal immune response to COVID-19 mRNA vaccination on the development of syncytiotrophoblast (STB), which forms the functional cell layer of the placenta where maternal-fetal exchange takes place.
Serum samples were collected from pregnant women before vaccination and after the second vaccination with the Pfizer-BioNTech mRNA vaccine (n=12 paired samples). Human trophoblast stem cells were subjected to in vitro STB differentiation in the presence of the serum samples. Cell morphology, proliferation and marker gene expression were assessed to determine the extent of STB differentiation.
All cells obtained an STB-like morphology, upregulated STB markers and downregulated trophoblast stem cell markers. We did not find any significant differences in the extent of differentiation between STBs treated with pre- and post-vaccination serum samples.
This in vitro study suggest that the maternal inflammatory response and the presence of SARS-CoV-2 antibodies in the maternal blood are not harmful to STB development of the placenta. These findings support the growing body of evidence that COVID-19 mRNA vaccination during pregnancy is safe.

Copyright © 2024. Published by Elsevier Ltd.