Objective To investigate the relationship between single nucleotide polymorphism (SNP) of transcription factor 7-like 2 (TCF7L2) at locus rs7903146,rs290487,rsl1196205,rs 12255372 and genetic susceptibility in women with gestational diabetes mellitus (GDM).Methods As a case-control study,100 pregnant women with GDM and 100 healthy pregnant women in the Maternal and Children Health Hospital of Jiangxi Province were recruited from January 2010 to July 2013.Clinical parameters,including body mass index (BMI),fasting insulin (FINS),fasting plasma glucose (FPG) and homeostatic model assessment-insulin resistance index (HOMA-IR) were measured after admission to hospital.Allelespecific PCR was used to analyze the SNP of TCF7L2 at locus rs7903146,rs290487,rs11196205,rs12255372.Results (1)The BMI,FPG,FINS and HOMA-IR in GDM group were(27.4±3.0) kg/m2,(5.6±1.0) mmol/L,(6.2±3.4) mU/L and 1.8± 1.0,and were (24.2±2.9) kg/m2,(5.3±0.8) mmol/L,(4.5±2.8) mU/L,1.2± 0.8 in the control group,respectively.The differences had statistically significance (P＜0.05).(2)The SNP of TCF7L2 gene,locus rs7903146 were CC,CT and TT genotype; the SNP of locus rs290487 were CC,CT and TT genotype; and the SNP of locus rs1 1196205 were GG and CC genotype; while the SNP of locus rs12255372 was GG genotype.(3)The distribution frequencies of genotype CC,CT and TT at locus rs7903146 in the GDM group were 40％ (40/100),36％ (36/100) and 24％ (24/100),respectively.While in the control group,they were 55％ (55/100),38％ (38/100) and 7％ (7/100),respectively.The frequencies of C and T allele of rs7903146 were 58％and 42％ in the GDM group,and in the control group they were 74％ (148/200) and 26％ (52/200).The differences of genotype distribution and C/T allele frequency of rs7903146 between the two groups were statistically significant (P＜0.05).(4)The distribution frequencies of genotype CC,CT and TT at locus rs290487 in the GDM group were 12 ％ (12/100),36 ％ (36/100) and 52％ (52/100),and were 16％ (16/100),34％ (34/100) and 50％ (50/100) in the control group.The frequencies of C and T allele of rs290487 were 30％ (60/200) and 70％ (140/200) in the GDM group,and were 33％ (66/200) and 67％ (134/200) in the control group.There was no difference of genotype distribution and C/T allele frequency of rs290487 between the two groups (P＞0.05).(5)The distribution frequencies of genotype GG and CC at locus rs1 1196205 in the GDM group were 99％ (99/100) and 1％ (1/ 100),while those in the control group were 100％(100/100) and 0％.The frequency of G and C allele of rs1 1196205 were 99％(198/200) and 1％(2/200) in the GDM group,while in the control group were 100％ (200/200) and 0.There was no difference of genotype distribution and G/C allele frequency of rs11196205 between the two groups (P＞0.05).(6)The distribution frequencies of genotype GG at locus rs12255372 were 100％(100/100) in both the GDM group and the control group.The frequencies of G allele of rs12255372 were 100％ (200/200) in both the GDM group and the control group.There was no difference of genotype distribution and G allele frequency of rs12255372 between the two groups (P＞0.05).(7)After adjusting for age,gestational age,BMI,FPG and FINS,pregnant women with TT genotype at locus rs7903146 were more likely to have hyperglycemia compared with the C allele carriers (OR=2.77,95％ CI:1.03-7.57,P＜0.05).Conclusions The polymorphism of locus rs7903146 in TCF7L2 gene may be associated with genetic susceptibility in women with GDM.TT genotype is likely to be risk factor in the pathogenesis of GDM.