Study of the relationship between VNTR polymorphism in intron 4 & Glu298Asp polymorphism in 7 exon of endothlial nitric oxide synthase gene and recurrent spontaneous abortion

Recent studies have indicated that genetic polymorphisms of the specific genes is one of the causes of miscarriage. In the other hand it is observed that nitric oxide (NO), as a signaling molecule, is participated in primary events of pregnancy such as implantation of blastocyte, differentiation of trophoblast, trophoblast invasion, and it enhances blood supply through the maternal arteries to the placenta thus it has a role in implantation and maintenance of pregnancy. NO is produced by endothelial nitric oxide synthase that is expressed in placenta, whereas this enzyme and its production play a key role in early stages of gestation, we investigated relationship between polymorphism of this gene and complication of pregnancy. In this study we used 100 women who had three or more constitutive miscarriage with unknown reason in first trimester of their pregnancy in case group. Control group is included 100 women with normal pregnancy. Both group were analysed for VNTR polymorphism in intron4 of endothelial nitric oxide synthase gene by PCR and also were analysed for Glu298Asp polymorphism in exon 7 of this gene by PCR-RFLP and sequencing. Genotype frequency of VNTR polymorphism in case group is 63% (bb), 33% (ab), 4% (aa) and in control group is 79% (bb), 18% (ab), 3% (aa). The genotype frequency of Glu298Asp polymorphism in exon7 is as follow: 71% (GG), 25% (GT), 4% (TT) in case group and 68% (GG), 29% (GT), 3% (TT) in control group.Our data indicate that the “a“allele frequency is significantly different between case and control group but other data do not show difference. Therefore a allele of VNTR polymorphism of endothelial nitric oxide synthase gene is a risk factor for RSA but T allele don’t have any role.