探讨亚甲基四氢叶酸还原酶(MTHFR)基因多态性与血清叶酸水平，对妊娠期糖尿病(GDM)患者及其妊娠结局的影响。

选择2016年12月至2018年12月，于青岛市城阳人民医院进行产前检查的568例GDM患者为研究对象，并将其纳入GDM组。选择同期在该院进行产前检查的674例健康孕妇纳入对照组。采用荧光定量聚合酶链反应(fqPCR)技术，分析所有受试者MTHFR基因C677T、A1298C位点基因型，同时检测其血清叶酸水平。采用χ²检验，对2组受试者MTHFR基因C677T及A1298C位点等位基因及基因型分布，以及不同妊娠结局GDM孕妇C677T位点基因型分布进行比较；采用t检验、单因素方差分析及最小显著性差异(LSD)-t检验，比较不同妊娠结局GDM患者血清叶酸水平，对2组MTHFR基因C667T位点3个基因型受试者的血清叶酸水平进行组内及组间比较；采用受试者工作特征(ROC)曲线，对C667T位点不同基因型联合血清叶酸水平，对于GDM预测价值进行分析。本研究遵循的程序经青岛市城阳人民医院伦理委员会批准[审批文号：(2015年)伦理批第(11)号)]，并与所有受试者签署研究知情同意书。

①GDM组受试者MTHFR基因C667T位点等位基因C的频率显著高于对照组(70.9% vs 61.5%，χ²＝24.483、P<0.001)，该位点基因型以CC为主，而对照组则以CT为主。2组受试者MTHFR基因A1298C位点的等位基因(A/C)及基因型(AA/AC/CC)分布比较，差异均无统计学意义(均为P>0.05)，并且2组均以A等位基因及AA基因型为主。②2组均为MTHFR基因C667T位点为CC、CT、TT 3种基因型受试者的血清叶酸水平比较，差异有统计学意义(P<0.05)，其中CC基因型受试者血清叶酸水平显著高于TT基因型者，并且差异有统计学意义(P<0.001)。③GDM组MTHFR基因C667T位点为CC、CT及TT基因型受试者的血清叶酸水平为(16.4±2.4) nmoL/L、(14.6±3.8) nmoL/L及(12.4±3.1) nmoL/L，均显著低于对照组的(20.4±2.5) nmoL/L、(18.5±3.4) nmoL/L及(16.3±3.0) nmoL/L，并且差异均有统计学意义(t＝28.040、19.292、22.869，均为P<0.001)。④MTHFR基因C667T位点不同基因型联合血清叶酸水平预测GDM的ROC曲线下面积为0.816(P<0.05)。⑤GDM组发生不良妊娠结局受试者MTHFR基因C667T位点CC基因型频率(32.5%)及血清叶酸水平[(13.3±4.2) nmoL/L]，均显著低于未发生不良妊娠结局者[42.3%、(15.9±4.0) nmoL/L]，而TT基因型频率(25.3%)则显著高于未发生不良妊娠结局者(17.8%)，并且差异均有统计学意义(χ²＝5.626、P＝0.018，t＝7.446、P<0.001，χ²＝4.680、P＝0.031)。

GDM患者MTHFR基因C667T位点CC基因型占比较高，并且血清叶酸水平较健康孕妇低。MTHFR基因C667T位点基因型和血清叶酸水平，与GDM患者的妊娠结局有关。

To investigate effects of methyleneterahydrofolate reductase (MTHFR) gene polymorphism and serum folic acid level on pregnant women with gestational diabetes mellitus (GDM) and their pregnancy outcomes.

A total of 568 pregnant women with GDM who underwent prenatal examination in Qingdao Chengyang People′s Hospital from December 2016 to December 2018 were selected as research objects, and they were included into GDM group. A total of 674 healthy pregnant women who underwent prenatal examination in the same period and same hospital were included into control group. Genotypes at locus C677T and A1298C of MTHFR gene in all subjects were analyzed by fluorescent quantitative polymerase chain reaction (fqPCR), meanwhile, their serum folic acid levels were detected. The alleles and genotype distributions of C677T and A1298C loci of MTHFR gene between two groups, also genotype distribution of C677T locus between pregnant women with different pregnancy outcomes in GDM group were compared by chi-square test. Serum folic acid levels between pregnant women with different pregnancy outcomes in GDM group were compared by independent-samples t test, one-way ANOVA and least significant difference (LSD)-t test were used to compare serum folic acid levels of subjects with 3 genotypes of MTHFR gene C667T loci within and between two groups. The predictive value of GDM through different genotypes of C667T locus combined with serum folic acid level were analyzed by receiver operating characteristics (ROC) curve. The procedures followed in this study were approved by the Ethics Committee of Qingdao Chengyang People′s Hospital [Approval No. (2015) Ethics Lot No. (11)]. All subjects signed the informed consents.

① The frequency of allele C at C667T locus of MTHFR gene in GDM group was significantly higher than that in control group (70.9% vs 61.5%, χ²=24.483, P<0.001), and the genotype of this locus was mainly CC, while that of control group was mainly CT. There were no significant differences in distribution of alleles (A/C) and genotypes (AA/AC/CC) of MTHFR gene A1298C locus between two groups (all P>0.05), and A allele and AA genotype were dominant in both groups. ② The results in both groups showed that the differences of serum folic acid levels of the subjects with CC, CT and TT genotype at C667T loci of MTHFR gene was statistically significant (P<0.05), and serum folic acid level of subjects with CC genotype was significantly higher than that with TT genotype, and the difference was statistically significant (P<0.001). ③ Serum folic acid levels of subjects with CC, CT and TT genotypes at C667T locus of MTHFR gene in GDM group were (16.4±2.4) nmoL/L, (14.6±3.8) nmoL/L and (12.4±3.1) nmoL/L, which were significantly lower than those of (20.4±2.5) nmoL/L, (18.5±3.4) nmoL/L and (16.3±3.0) nmoL/L in control group, and the differences were statistically significant (t=28.040, 19.292, 22.869; all P<0.001). ④ The area under the ROC curve for prediction of GDM by different genotypes of MTHFR gene C667T locus combined with serum folic acid level was 0.816 (P<0.05). ⑤ The CC genotype frequency of MTHFR gene C667T locus and serum folic acid level of subjects with adverse pregnancy outcomes in GDM group were 32.5% and (13.3±4.2) nmoL/L, which were significantly lower than those of 42.3% and (15.9±4.0) nmoL/L of subjects without adverse pregnancy outcomes, and the TT genotype frequency (25.3%) was significantly higher than that of subjects without adverse pregnancy outcomes (17.8%), and the differences were statistically significant (χ²=5.626, P=0.018; t=7.446, P<0.001; χ²=4.680, P=0.031).

Proportion of CC genotype at MTHFR gene C667T locus was higher in pregnant women with GDM, and their serum folic acid level was lower than that of healthy pregnant women. Genotype at MTHFR gene C667T locus and serum folic acid level were associated with pregnancy outcome of GDM pregnant women.