Objective To investigate the relationship between expressions of alpha 2-HS-glycoprotein (AHSG) gene mRNA and protein in placenta and insulin resistance in patients with gestational diabetes mellitus (GDM).Methods The expressions of AHSG gene mRNA and protein in placenta were detected by reverse transcriptase-polymerase chain reaction (RT-PC R) and Western blot technique in normal uterogestation uterine-incision delivery patients (control group,43 cases) and patients with GDM (GDM group,45 cases).Fasting plasma glucose (FPG) and fasting insuhn (FINS) were detected before uterine-incision delivery,and the homeostasis model of assessment for insulin resistance index (HOMA-IR) was computed.Results The FPG,FINS and HOMA-IR in GDM group were significantly higher than those in control group [(5.28 ± 0.63)mmol/L vs.(4.24 ±0.21) mmol/L,(11.75 ±4.85) mU/L vs.(9.73 ±2.18) mU/L,2.79 ±1.02 vs.1.87 ± 0.66],there were statistical differences (P ＜ 0.01 or ＜ 0.05).The expressions of AHSG gene mRNA and protein in GDM group were significantly higher than those in control group (0.761 6 ± 0.069 1 vs.0.329 4 ± 0.025 1 and 0.824 5 ± 0.137 5 vs.0.420 3 ± 0.075 0),there were statistical differences (P＜ 0.01or ＜ 0.05).HOMA-IR level in GDM group was positively correlated with AHSG gene mRNA and protein (r =0.633,0.587,P ＜0.05).Conclusions The expressions of AHSG gene mRNA and protein are significantly higher in patients with GDM.Insulin resistance may play an important role in the pathogenesis and development of GDM.