Increasing evidence supports a role for altered T helper 1 (Th1)-Th2 cytokine balance in idiopathic recurrent spontaneous abortion (RSA). The aim of this study was to investigate the association of the interleukin 10 (IL-10) promoter polymorphisms -592C/A, -819C/T and -1082A/G with RSA. Women (n = 350) with at least three consecutive spontaneous abortions (RSA cases) and 200 control women with at least two successful pregnancies were included. The frequency of the -819T allele [P = 0.05, odds ratio (OR) = 1.51], but not other single-nucleotide polymorphisms (SNPs), was higher among RSA patients. Complete linkage disequilibrium (LD) was seen between -592C and -819C and -1082G alleles, as well as between -592A and -819T and between -819C and -1082G alleles only among patients. Although the genotype frequencies (except for -819C/C) of the three polymorphisms were comparable between patients and controls, higher frequency of -592A/-819T/-1082A haplotype (OR = 4.01, 95% CI = 1.83-7.95) was seen in cases versus controls. Regression analysis indicated that, after adjusting for potential variables, -592C/A (OR = 3.32, 95% CI = 1.76-6.27) and -819C/T (OR = 5.06, 95% CI = 2.59-9.91) were associated with exclusively early but not exclusively late RSA, where negative association for both was noted. This supports the notion of involvement of IL-10-592C/A and -819C/T polymorphisms as inherited risk factors of idiopathic RSA.