Fig. 2

Differentially regulated metabolites across term and preterm births. The figure presents volcano plots and boxplots illustrating metabolite differences across study groups. Panels (a–b) display volcano plots based on univariate linear regression analysis for the following comparisons: (a) term birth vs. overall preterm birth, (b) term birth vs. non-infectious preterm birth. Panel (c) shows the boxplot of 9-HODE, highlighting its distribution across study groups. Panels (d–e) present volcano plots for (d) term birth vs. infectious preterm birth and (e) non-infectious preterm birth vs. infectious preterm birth. Panel (f) shows the boxplot of cLPA(18:1) which was statistically significant in the non-infectious vs. infectious preterm birth comparison. In all volcano plots, the x-axis represents the regression estimate and the y-axis depicts statistical significance (-log₁₀ p-value). Metabolites are color-coded by compound classes, including bile acids, fatty acids, lysophospholipids, and oxylipins. Data points are shaped to indicate significance levels: significant after FDR correction, significant before FDR correction, and not significant. The vertical dashed line indicates an estimate of zero effect, and horizontal dashed lines denote significance thresholds. In each boxplot, the central line represents the median, with box edges denoting the interquartile range. Individual data points represent osmolality-normalized, log₂-transformed metabolite area ratio in each sample, and the black diamond represents the mean. The letters denote significance between groups from the linear-mixed effect models: shared letters indicate no significant difference (p > 0.05), while unique letters indicate significant difference (p < 0.05). FDR = False Discovery Rate; IP = infectious preterm; NIP = non-infectious preterm; T = term.