Demographic and clinical characteristics of GDM and controls
Subjects were categorized into 919 GDM patients and 1177 controls. Demographic and clinical data of different groups were summarized in the supplemental table.
Both groups had similar age distribution, times of gravidity, and number of abortions. The mean age of cases and controls was 30.71±4.18 and 30.75±4.21 years old. However, in GDM group, weeks of admission and delivery intended to be earlier (P<0.001) and the weight gain of newborns was heavier than in the control group as expected (P<0.001).
TGF-β1 and TGF-β3 polymorphism analysis
The subjects of the control group enrolled in this study were in accordance with HWE for these SNPs and displayed a group representative at the significance level of P>0.05.
The distributions of the genotypes and alleles in GDM cases and controls were reported in Table 1. We observed a statistically significant difference between GDM and healthy women in the frequencies of TGF-β3 rs2284792 (χ² =9.064, P =0.011). However, no statistical differences were detected either in TGF-β1 rs4803455 or in TGF-β3 rs3917201 between two groups in terms of genotypic frequencies. As shown in Table 1, the allelic frequencies of rs2284792 between two groups were not obviously different (χ² =1.592, P =0.207, OR=1.082, 95%CI 0.957-1.224). When categorized into three models (AA vs AG+GG, GG vs AG+AA and AG vs GG+AA), there was a significant difference between these two groups (For AA vs AG+GG model, χ²=6.314, P=0.012, OR 1.270, 95%CI 1.054-1.530; For AG vs GG+AA model, χ²=8.545, P=0.003, OR=0.773, 95%CI 0.650-0.919). Consistently, allelic frequencies of TGF-β1 rs4803455 or TGF-β3 rs3917201 were statistically insignificant.
TGF-β1 and TGF-β3 polymorphism analysis between GDM patients with and without PE
To further study the association between variants of the three SNPs and complications, samples were categorized into GDM cases with and without PE. The distributions of the genotypes and alleles in GDM patients with and without PE are shown in Table 2 and Table 3.
In GDM cases without PE group, the statistical difference between cases and controls in genotypic distributions of TGF-β3 rs2284792 was observed (χ²=9.774, P =0.008). Also, the same was found for allelic frequencies in AA vs AG+GG (χ²=8.476, P =0.004 OR=1.427, 95%CI 1.122-1.813) and AG vs GG+AA (χ²=7.842, P =0.005 OR=0.734, 95%CI 0.590-0.912). In contrast to TGF-β3 rs2284792, no obvious difference was found in either the genotypic distributions or allelic frequencies of TGF-β1 rs4803455 and TGF-β3 rs3917201 among GDM only cases.
In GDM cases with PE group, however, no obvious difference was found in either the genotypic distributions or allelic frequencies of three SNPs (for rs4803455, χ²=1.266, P =0.531 by genotype, χ2 =0.069, P =0.793, OR =1.021, 95%CI 0.873-1.194 by allele; when for rs2284792, χ2 =3.619, P =0.164 by genotype, χ2 =0.021, P =0.885, OR =1.011, 95%CI 0.867-1.1791by allele; and for rs3917201, χ2 =0.359, P =0.836 by genotype, χ2 =0.015, P =0.903, OR =1.009, 95%CI 0.867-1.175 by allele).
Analysis of Genotype-Phenotype Relationship
Analysis of the relationship between the genotypes of TGF-β3 rs2284792 and demographic characteristics among total GDM patients was shown in Table 4. However, no statistical differences were found for the genotype-phenotype relationship of rs2284792.