To our knowledge, this is the first investigation to explore both genome-wide and transcriptome-wide profiles in prospectively collected, mid-trimester maternal blood samples (from a well-defined cohort, using a PTB cut-off of ≤ 34 weeks gestation), to determine biomarkers of spontaneous preterm birth phenotypes PPROM and SPTB. Here, SPTB is linked to preterm premature rupture of the membranes.