LIF and COVID-19: At the same time, basic fibroblast growth factor (FGF), leukemia inhibitory factor (LIF), granulocyte colony-stimulating factor (G-CSF), platelet-derived growth factor subunit B (PDGF-BB), and other growth factors were also significantly lower in COVID-19-positive pregnant women than pregnant women without COVID-19 (Chen G. et al., 2021).