*2.1. Characteristics of the Control and Study Group*

The results of the study were obtained from 18 placentas taken from women with fetal growth disorders and from 18 control placentas. The clinical characteristics along with anthropometric measurements of mothers and their newborns are presented in our previous study, as in Table 1 [27].

There were no statistically significant differences between the research groups in terms of age, height, fertility, BMI prior to pregnancy and body weight before pregnancy and at delivery. The only statistically significant difference between the two groups was that the control group gained significantly more weight during pregnancy than the experimental group (*p* = 0.032). In the study group, the mean pulsation index (PI) in the gestational uterine arteries was statistically substantially greater than in the control group (*p* = 0.025), as was the PI in the arterial umbilical cord of fetuses with FGR compared to eutrophic fetuses (*p* = 0.0001). The CPR was substantially greater in the control group than in the study group (*p* = 0.0005). Women in the experimental group gave birth much earlier than those in the control group (*p* = 0.001). Compared to neonates from the control group, infants with FGR had a lower birth weight (*p* = 0.0001), shorter body length (*p* = 0.001), and poorer Apgar score in the first minute of life (*p* = 0.002).

#### *2.2. Analysis of the Bacterial Proteome in the Study and Control Groups*

In both groups, we considered an ns prot score ≥ 60 as a cut-off value for the detected protein's agreement with its theoretical equivalent. Based on the analysis of the proteinogram in the material collected from people from the study group (n = 18), 166 bacterial proteins were detected. Of these, 21 proteins had an emPAI value of 0 and were not included in further analysis. Out of the remaining 145 proteins, 52 were also present in the material from the control group (the differences in their content in individual materials are presented in Figures 1 and 2, and Tables 2 and 3). The remaining 93 proteins were present only in the material collected from the study group (their content in the material is shown in Figure 3B,D,F and Supplementary Figure S1B,D).


**Table 1.** Clinical characteristics and anthropometric measurements of mothers and newborns.

Values are shown as median (interquartile range) or mean ± standard deviation; statistical analysis was performed using a Mann–Whitney U test. Body mass index (BMI), pulsatility index (PI), umbilical artery (UA), middle cerebral artery (MCA), uterine artery (Ut A), cerebro-placental ratio (CPR), \*—statistically significant results.

**Figure 1.** Venn diagram showing the proportion between the number of proteins (for which emPAI values > 0) identified only in the material representing the control or study group and present simultaneously in both types of the samples.

**Figure 2.** Bar graphs showing the comparison of proteins present in both the test group and the control group. Statistically significant results that remained significant after applying the Bonferroni correction are marked with a red square. Graph showing protein content comparisons for which emPAI values were: significantly higher in the study group compared to control (**A**); significantly higher in control compared to the study group (**B**); not significantly higher in the study group compared to the control (the results, however, trend toward significance) (**C**); not significantly higher in the study group compared to control (**D**); not significantly higher in control compared to study group (**E**). Expressions from Figure 2 are explained in Table 2.

**Table 2.** Legend to Figure 2.



#### **Table 2.** *Cont.*
