Lower frequency of the HLA-G UTR-4 haplotype in women with unexplained recurrent miscarriage

HLA-G expressed by trophoblasts at the fetal-maternal interface and its soluble form have immunomodulatory effects. HLA-G expression depends on the combination of DNA polymorphisms. We hypothesized that combinations of specific single nucleotide polymorphisms (SNPs) in the 3'untranslated region (3'UTR) of HLA-G play a role in unexplained recurrent miscarriage. In a case control design, 100 cases with at least three unexplained consecutive miscarriages prior to the 20th week of gestation were included. Cases were at time of the third miscarriage younger than 36 years, and they conceived all their pregnancies from the same partner. The control group included 89 women with an uneventful pregnancy. The association of HLA-G 3'UTR SNPs and specific HLA-G haplotype with recurrent miscarriage was studied with logistic regression. Odds ratios (OR) and 95% confidence intervals (95% CI) were reported. Individual SNPs were not significantly associated with recurrent miscarriage after correction for multiple comparisons. However, the presence of the UTR-4 haplotype, which included +3003C, was significantly lower in women with recurrent miscarriage (OR 0.4, 95% CI 0.2-0.8, p = 0.015). In conclusion, this is the first study to perform a comprehensive analysis of HLA-G SNPs and HLA-G haplotypes in a well-defined group of women with recurrent miscarriage and women with uneventful pregnancy. The UTR-4 haplotype was less frequently observed in women with recurrent miscarriage, suggesting an immunoregulatory role of this haplotype for continuation of the pregnancy without complications. Thus, association of HLA-G with recurrent miscarriage is not related to single polymorphisms in the 3'UTR, but is rather dependent on haplotypes.