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which enabled the differentiation and relative quantification of proteins between samples, including their phosphorylation levels. Results: The TMT system detected 2675 proteins and 778 phos-phorylated peptides. Compared with the uninfected placenta, in the infected placentae, several essential pathways, including the innate and acquired immune systems, were upregulated. The phosphorylation levels of these pathways were also activated. The complement cascade, VEGF signaling, and RHO GTPase signaling were also changed. In patients with IUFD, SARS-CoV-2 infection-related pathways were still enriched in the placentae, while the effects of postmortem tissue degradation could not be ruled out. Conclusion: SARS-CoV-2 infection during pregnancy affects placental protein expression and phosphorylation. SARS-CoV-2 infection must cause both histopathological and functional changes in the placenta in addition to direct cytotoxicity. Analysis of the local immune responses and mechanisms of the placental barrier enables the rescue of placental dysfunction in infected mothers and subsequent fetal well-being.