Evidence of a gene-environment interaction that predisposes to spontaneous preterm birth: a role for asymptomatic bacterial vaginosis and DNA variants in genes that control the inflammatory response

Objective: We determined whether an environmental exposure to bacterial vaginosis (BV) modified genetic susceptibilities for spontaneous preterm delivery within genes that regulate the inflammatory response. Study Design: Maternal DNA samples and vaginal smears for Gram staining were collected from 743 women (68 preterm births). We used a 1536-single nucleotide polymorphism (SNP) custom chip to study associations between genotype distributions and preterm birth. Results: For 8 SNPs in 3 genes (protein kinase C alpha, fms-like tyrosine kinase 1, and interleukin 6), the odds ratios for preterm birth ranged from 1.9-4.0 among women with susceptible genotypes who were BV positive. The odds ratios for preterm birth were 2.0-5.0 times greater among women who were BV positive than among women who were BV negative. The significance of these differences was demonstrated by logistic regression analyses for genotype/BV interaction. Conclusion: These results demonstrate that the risk of preterm delivery that is associated with tag SNPs in genes that regulate the inflammatory response is modified by an environmental exposure such as bacterial vaginosis.