CMV infection of the cytotrophoblast progenitor cells associated with floating villi in the placenta appears to elicit a shift in the Th1-type cytokine and Th2-type cytokine (Th1/Th2) ratio balance of amniotic fluid and placental tissues towards a Th1 profile by upregulation of proinflammatory cytokines like monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor (TNF) [105,106]. This evidence concerns the gene CCL2 and cytomegalovirus infection.