Success rate in human pregnancies is believed to be very low and sex-specific mechanisms may operate in prenatal loss. Assuming a sex-differential in prenatal loss exists, we examined genetic markers in biologically plausible targets in the HLA complex, other immune system-related and iron-regulatory genes in 388 healthy newborns from Wales (UK) using one sex as a control group for the other. Genotyping of 333 single nucleotide polymorphisms (SNPs) from 107 genes was achieved mainly by TaqMan

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... says. Twentytwo of autosomal SNPs showed frequency differences between 187 male and 201 female newborns either individually or as part of a haplotype. Of these, six markers (RXRB rs2076310, HLA complex haplotype HLA-DQA1 rs1142316-HLA-DRA rs7192-HSPA1B rs1061581, HIST1H1T rs198844, IFNG rs2069727, NKG2D rs10772266 and IRF4 heterozygosity) showed statistically robust differences between male and female newborns and multivariable modeling confirmed their independence. There were fewer males homozygote for combined wildtype genotypes of LIF rs929271, TP53 rs1042522 and MDM2 rs2279744 compared with females [OR ¼ 0.3, 95% confidence interval (CI) ¼ 0.1-0.8; P , 0.01] although these SNPs did not show any association individually. It is unlikely that SNPs have clinical utility as single markers in any trait with complex etiology but polygenic predictive models remain a possibility. If their validity is confirmed in larger studies of different populations and functional mechanisms of these preliminary associations are elucidated, these markers from the HLA complex, NKG2D region and cytokines may cumulatively have sufficient predictive value for susceptibility to prenatal selection in each sex.