To investigate maternal whole blood gene expression profiles associated with spontaneous preterm birth (SPTB, <37 weeks) in asymptomatic pregnant women. The ‘All Our Babies’ (AOB) community based cohort in Calgary recruited pregnant women between May 2008 and December 2010. Maternal blood at 17-23 (time point 1, T1) and 27-33 weeks of gestation (T2) were collected. Fifty-one SPTBs were matched to 114 term delivery controls. Microarray was performed on 326 samples from 165 women. Univariate analyses determined significant clinical factors and differential gene expression associated with SPTB. Thirteen genes were validated using qRT-PCR. Three multivariate models were constructed to identify gene expressions associated with SPTB at T1 (Model A) and T2 (Model B), and temporal gene expressions (T2-T1) associated with SPTB at T2 (Model C).