ABSTRACT. Endothelial nitric oxide synthase (eNOS) is an enzyme that influences placental human chorionic gonadotropin production during gestation. Previous studies have indicated an association between eNOS activity, implantation, and maintenance of pregnancy, but proposed associations between polymorphisms of the eNOS gene and recurrent miscarriage (RM) are controversial. To identify markers contributing to the genetic susceptibility to RM, we examined the potential association between RM and 8 single nucleotide polymorphisms (SNPs; rs1799983, rs2070744, rs11771443, rs3918188, rs2853796, rs7830, rs1541861, and rs2853792) of the eNOS gene using the MassARRAY system (Sequenom, USA). The enrolled participants included 192 RM patients and 201 women with normal fertility as controls. The results showed that rs1799983 at exon 7 of the eNOS gene was significantly associated with RM (genotype: chi-square = 15.071, P = 0.001; allele: chi-square = 6.250, P = 0.016). Another significant association was observed for rs11771443 in the promoter (genotype: chi-square = 6.259, P = 0.044; allele: chi-square = 7.076, P = 0.008). Furthermore, strong linkage disequilibrium was observed in 3 blocks (Dꞌ > 0.9), and significantly fewer T-T-G haplotypes (chi-square = 5.981, P = 0.015) residing in block 1 were found in RM patients. These findings point to a role for eNOS gene polymorphisms in RM in the Chinese Han population and may be informative for future genetic or neurobiological studies of RM.

ABSTRACT. Despite more than a century of intensive study, the mechanisms of successful pregnancy remain unclear. Recent research suggests that NF-κB (nuclear factor kappa B) plays an important role in embryo implantation. In the current study, we aimed to identify SNPs that contribute to genetic susceptibility for recurrent implantation failure (RIF). Thus, we examined the potential associations between RIF and ten SNPs (rs28362491, rs3774932, rs1598856, rs230528, rs230521, rs3774956, rs4648055, rs3774964, rs4648068, and rs3774968) of the NF-κB gene. Participants included 209 patients with RIF and 395 controls. Our results revealed that there were statistically significant differences observed in the allelic and genotypic frequencies of the rs28362491 promoter in the NF-κB gene. The frequency of the del/ del genotype was significantly higher in RIF patients than in healthy controls (P = 0.004). Compared with healthy controls, the RIF patients carried a higher frequency of the rs28362491 del allele (P = 0.010). Furthermore, strong linkage disequilibrium was observed in the three identified haplotype blocks (D' > 0.9). Particularly, in block 1 (rs230528-rs230521), the A-C haplotype occurred significantly more frequently (P = 0.029) in subjects with RIF (P = 0.0003). In contrast, the A-G haplotype occurred significantly less frequently (P = 0.008) in RIF subjects. These findings support an important role for G-712A polymorphisms of NF-κB in RIF, and may guide future studies that aim to characterize genetic risk factors for RIF.