(A) Plot of log₂ ratio to average baseline (TNL) expression for the 4814 transcripts differentially abundant (FDR < 0.1, minimum fold-change ± 1.5, DESeq2 algorithm) between term myometrial specimens in the absence (TNL, n = 5) or presence (TL, n = 5) of labor. Transcripts with increased abundance are depicted in red, while those with decreased levels are shown in blue. (B) Correlation matrix with unsupervised hierarchical cluster analysis showing a higher degree of similarity among samples within each cohort (blue circles, TNL; red squares, TL) than between cohorts when considering the differentially abundant transcripts. (C) Scree plot of principal components following application of PCA to the differentially expressed genes in term myometrial specimens. The first principal component, PC1, accounted for most (57%) of the explained variance in the data. (D) Scatterplot of PC1 and PC2 with accompanying box-and-whisker plots (below) showing the distribution of TL (red squares), TNL (blue circles), and preterm birth (PTB, gray symbols) in PC space based on the expression signature of 4184 transcripts. Spontaneous initiation of PTB is denoted by light gray boxes, while dark gray circles indicate the absence of spontaneous labor initiation as determined clinically. (E) Scatterplot as in D but recolored to indicate in greater detail the clinical disposition of the pregnancies from which the PTB myometrial specimens were derived: intact membranes with Triple I (green squares); intact membranes without Triple I (Group 5, PTB-PI, yellow circles); preterm premature rupture of membranes (PPROM) with Triple I (pink squares); and PPROM without Triple I (purple squares). Two clusters comprising mostly nonquiescent (NQ) and quiescent (Q) myometrial specimens were evident (dashed circles). PTB cases with complex mixed phenotypes (MY25 and MY28), as well as a NQ specimen (MY31) that distributed between the term specimen clusters, are indicated.