Experimental models have provided mechanistic evidence that blockade of C5a, C5a receptor (C5aR), Factor B, C3, or C6 in non-infection models protects against fetal lethality and IUGR (Holers et al., 2002; Girardi et al., 2006b; Lynch et al., 2011; Singh et al., 2011). This evidence concerns the gene C5AR1 and fetal growth restriction.