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Introduction: Maternal SARS-CoV-2 infection can affect pregnancy outcome, but the placental response to and the effect of timing of infection is not well studied. The aim of this study was to investigate the placental levels of inflammatory and cardiovascular markers in pregnancies complicated by SARS-CoV-2 infection compared to non-infected pregnancies, and to investigate whether there was an association between time point of infection during pregnancy and placental inflammatory and cardiovascular protein levels.

Methods: Placental samples from a prospectively recruited pregnancy cohort of SARS-CoV-2-infected (n = 53) and non-infected (n = 50) women were analysed for 177 inflammatory and cardiovascular proteins, using an antibody-based proximity extension assay. In the SARS-CoV-2-infected group, half of the women were infected before 20 weeks of gestation, and five women were hospitalised for severe SARS-CoV-2 infection. Single-protein analyses were performed with linear mixed effects models, followed by Benjamini-Hochberg correction for multiple testing. Multi-protein analyses were performed using principal component analysis and machine learning algorithms.

Results: The perinatal outcomes and the placental levels of inflammatory or cardiovascular proteins in women with SARS-CoV-2 infection were similar to those in non-infected women. There were no differences in inflammatory or cardiovascular protein levels between early and late pregnancy SARS-CoV-2 infection, nor any linear correlations between protein levels and gestational age at time of infection.

Discussion: Women with SARS-CoV-2 infection during pregnancy without clinical signs of placental insufficiency have no changes in inflammatory or cardiovascular protein patterns in placenta at time of birth regardless of the timing of the infection.