We examined the association of 166 single nucleotide polymorphisms (SNPs) in cytokines and cytokine related genes with cytokine concentrations (IL-1beta, IL-8, and IL-10) in the amniotic fluid (AF). These cytokines have been associated with spontaneous preterm birth (PTB) and their genetic regulation may play a role in disease risk. These associations were studied in both PTB and term births in African Americans and Caucasians; maternal and fetal genotypes were studied separately. Analyses modeled genotype, pregnancy status, and marker by pregnancy status (case/control) interaction with cytokine concentration as outcome. Our results indicate that AF cytokines (IL-1beta and IL-10) were associated with interactions between pregnancy status and both maternal and fetal SNPs, with the most significant interactions being observed for African Americans with IL-1beta concentration (maternal at IL1RAP rs1024941 p < 10(-3), fetal IL1RAP rs3773953 p < 10(-3)). AF IL-10 concentrations also showed evidence for association with SNPs in both ethnicities with the most significant interaction in Caucasian maternal samples (IL10 rs1800896 p < 10(-3)). Our data indicate that the genetic regulation of cytokine concentrations in PTB likely differs by ethnicity. AF cytokine concentrations were associated with interactions between genotype and PTB in African Americans, but less so in Caucasians.