Figure 2: Macrophage polarization and M1/M2 macrophages during pregnancy.

Macrophages polarize to M1 and M2a, M2b, M2c, and M2d phenotypes under different cytokine milieu (A). Macrophages display different phenotypes during pregnancy. M1 macrophages are dominant during peri-implantation stage. M1 and M2 both phenotypes are present during implantation and early 1^st trimester. M2 phenotypes predominate during late first trimester and maintenance of pregnancy during 2^nd trimester. M2 begin to decline and M1 again increase during 3^rd trimester and parturition (B).