Abstract： Objective To investigate the different expressions of various subtypes of human leukocyte antigen-G(HLA-G)mRNA in placentas among early and late-onset severe preeclamptic and normal pregnant women. Methods Eleven placental samples from early-onset severe preeclamptic pregnancies and fourteen from late-onset severe preeclamptic pregnancies were collected as study group;eight placental samples from normal pregnancies were collected as control group.The levels of HLA-G mRNA in the three groups were measured by nested RT-PCR. Results Compared with the counterparts in the control group,the leveI of HLA-G1 subtype was significantly decreased (median:Early-onset group:1.37,P<0.05;Late-onset group:24.90,P<0.05;Control group:46.67,P<0.05)and the level of HLA-G5 subtype increased(median:Early-onset group 19.23;Late-onset group:3.65;Control group:1.33)in both early and late-onset severe preeclamptic group.The level of HLA-G2 subtype increased(median:Early-onset group:0;Late-onset group:21.59,P<0.05;Control group:5.39)in the late-onset severe preeclamptic group. Conclusion The reduced expression of HLA-G membrane-bound subtype mRNA in the placenta and the increased expression of HLA-G soluble subtype mRNA in the placenta may be related tO the pathogenesis of preeclampsia.