CTLA4 and cytomegalovirus infection: Figure 3A staining demonstrated significant infiltration of LAG3+ cells in VUE compared to controls (49 vs. 0.2 cells/image; p=0.05). However, there was a high level of variability noted across the VUE cases (0-116 cells/image; Figure 3B). We did not see evidence of a difference in LAG3+ cells between VUE and CMV infection (49 vs. 7 cells/image; p=0.399), and CMV infection and control cases (7 vs. 0.2 cell/image; p=0.40). In contrast, overall expression of CTLA4+ cells in the placental villi was negative in all three groups, with only a few fetal macrophages staining positive (Figure 4).