Aim: the primary objective of this study was to improve the pathomorphological diagnosis of macrosomia in stillborn fetuses. This was achieved by analyzing the characteristics of collagen synthesis in the structural components of the blood-thymus barrier in macrosomic stillborn fetuses and relating these findings to specific anthropometric parameters.

Material and methods. Our study examined 34 thymus specimens from macrosomic stillborn fetuses, which we divided into three groups (SF1, SF2, SF3) based on their Height and Weight Index (HWI). Group of medium-weight fetuses, randomly selected as the control group (SFc) (n = 9). Research methods: histological, immunohistochemical, morphometric. Statistical analysis was performed in accordance with the current methodological requirements.

Results. In endothelial basement membranes the synthesis of type IV collagen was significantly reduced in macrosomes fetuses of the SF1 group (p ≤ 0.05), with a tendency to increase in macrosomes of the SF3 group. In epithelial basement membranes, there was a significant increase in the production of type IV collagen in the thymus of SF3 group (p ≤ 0.05) and a tendency toward a decrease in the expression of this collagen in SF1 group of macrosomes. Compared to the control, in the reticular fibers and amorphous substance of the blood-thymus barrier the optical density of the luminescence of type III collagen was maximal in observations of the SF3 group and minimal in large fetuses of the SF1 group.

Conclusions. In the structure of the blood-thymus barrier of large fetuses, the expression of type IV collagen was detected in the composition of the epithelial and endothelial basement membranes. Vascular basement membranes contained a greater amount of type IV collagen compared to the epithelial basement membranes of blood-thymus barrier, depending on the anthropometric characteristics of the fetuses. In the reticular fibers and amorphous substance of the blood-thymus barrier of stillborns, irrespective of their anthropometric characteristics, type III interstitial collagen was detected.