Single nucleotide polymorphisms in the promoter region of the interleukin-6 gene and the risk of recurrent pregnancy loss in Japanese women.

OBJECTIVE

To investigate the relationships between recurrent pregnancy loss and single nucleotide polymorphisms (-634C-->G and -174G-->C genotypes) in the promoter region of the interleukin (IL)-6 gene in the Japanese population.

DESIGN

A case-control study.

SETTING

Obstetrics and gynecology department of a university hospital.

PATIENT(S): Cases were 76 women with recurrent pregnancy loss; controls were 93 fertile women.

INTERVENTION(S): Determination of IL-6 promoter gene polymorphisms performed by polymerase chain reaction and gel electrophoresis.

MAIN OUTCOME MEASURE(S): Frequency and distribution of the promoter region of the IL-6 gene allele.

RESULTS

There was a significant difference in the -634C-->G genotype frequency (CC vs. CG/GG) between women with recurrent pregnancy loss and controls. The risk of recurrent pregnancy loss was lower in the carriers of the G allele than in women with the wild type (CC) (odds ratio = 0.46; 95% confidence interval = 0.24-0.91). On the other hand, we did not detect any carrier of -174C among the 169 subjects.

CONCLUSION(S): The results suggest that, in the Japanese population, women carrying the -634G allele of the IL-6 gene might have a decreased risk of recurrent pregnancy loss.