Diversified intrauterine microbiome may modify the environment of the developing fetus with possible short- and long-term impact on the individual's health and disease. Meconium which provides the individual-specific information about the intrauterine microbiome composition is a biological material with potential uses in routine clinical diagnostic practice.

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Aim: The proteins accumulated in the meconium reflect the intrauterine environment and are naturally excreted by a neonate. The identification and classification of individual meconium proteins may be a valuable source of information about physiological and pathological processes in utero. Methods: Proteomic analysis was used to study the protein composition in pooled 50 serial meconium portions from 10 neonates. The proteins were classified based on the gene ontology database. The amounts and relative number of proteins (%) in the identified categories and their subcategories were assessed. Results: A total of 946 proteins identified in meconium, including 430 represented by two or more peptides were classified into three categories: biological process (n = 401), molecular function (n = 386) and cellular component (n = 422). The highest number of proteins (>25% of the total) was found in the subcategories: developmental processes, signaling, transport, response to stimulus, regulation, metabolic processes, ion binding, extracellular region, membrane and cytoplasm. Conclusion: The composition of meconium proteins identified in this study may be a rich source of new biomarkers for use in neonatology with a potential to predict later development.

Calprotectin, lactoferrin, myeloperoxidase and PMN-elastase concentrations in meconium are interrelated. These proteins may serve as objective biomarkers describing and/or assessing the intrauterine environment.

Neutrophil gelatinase-associated lipocalin (NGAL) and lactoferrin (Lf) are among the key components of the innate immune system due to their ability to bind iron with high affinity and thus control inflammation. The aim of this study was to test the use of NGAL and LF measurements in meconium for the assessment of the intrauterine homeostasis. NGAL and Lf concentrations were measured using ELISA kits in all serial meconium portions (n = 81) collected from 20 healthy neonates. Mean ± SD meconium concentration of Lf was 45.07 ± 78.53 µg/g and more than 1000-fold higher compared with that of NGAL at 1.93 ± 2.46 ng/g. The correlation between the two proteins (r = 0.83, p < 0.0001) was found only for portions with Lf concentrations > 25 μg/g. High variability of NGAL and Lf concentrations in meconium and their correlations prove their key role as biomarkers of the fetal condition in utero. NGAL and Lf measured in meconium are candidate biomarkers for fetal iron status.