The objective was to investigate the association between idiopathic recurrent spontaneous abortion (RSA) and 3 SLC19A1 polymorphisms (-43T>C, 80G>A, and 696C>T). DNA from 269 patients with RSA and 125 controls were genotyped for the 3 SLC19A1 single nucleotide polymorphisms (SNPs) by polymerase chain reaction-restriction fragment length polymorphism. Homocysteine and folate levels of 100 patients with RSA were available for analysis. The combination genotypes of SLC19A1 -43TC/80GG, -43TC/80AA, and -43CC/80GA; 80GA/696TT, 80AA/696CC; and -43TC/696CC were less frequent in patients with RSA compared to controls (P < .05 for each). The -43C/80A/696 T and -43T/80G/696C haplotypes were more frequent in patients than controls, whereas -43T/80A/696C, -43C/80A/696C, -43C/80G/696C, -43C/80G/696T, and -43T/80G/696T haplotypes were less frequent in patients (P < .05 for each). The -43T/80G and 80A/696T haplotypes were more frequent in patients, while -43T/80A, -43C/80G, 80A/696C, 80G/696T, and -43C/696C haplotypes occurred less frequently in patients (P < .05 for each). The associations between idiopathic RSA occurrence and SLC19A1 -43T>C/80G>A/696C>T polymorphisms were identified and can be developed as biomarkers for RSA risk.