Comparative Metabolomic Profiling of Amino Acids in Dried Blood Spots from Dichorionic and Monochorionic Twins Complicated by Selective Fetal Growth Restriction and Twin-to-Twin Transfusion Syndrome

Multiple pregnancy is associated with a high risk of perinatal complications, among which twin-to-twin transfusion syndrome (TTTS) and selective fetal growth restriction (sFGR) are of particular importance. These conditions are specific to monochorionic twins, yet their metabolic consequences in newborns remain poorly understood. Dried blood spots (DBSs) represent a convenient and non-invasive biomaterial for metabolomic analysis. This study included 7 twin pairs with sFGR, 10 pairs with TTTS, and 16 pairs from uncomplicated pregnancies. The amino acid profile in DBSs was determined by HPLC–MS/MS. Statistical significance of variation in normalized intra-pair difference in amino acid levels (ΔS_twins) was assessed using the Mann–Whitney U test with Benjamini–Hochberg false discovery rate correction. The dynamics of ΔS_twins between birth and the corrected full-term age were analysed. In comparing sFGR group with controls, intra-pair differences for glycine and alanine were altered at birth, and for β-alanine and leucine at the second time point. In the TTTS group, deviations from controls were observed for glutamine (at the second time point) and for alanine, α-aminobutyric acid, and aspartic acid (in terms of dynamics). Direct comparison between the two pathologies revealed differences in citrulline (TTTS vs. sFGR at birth) and in several amino acids over time (valine, leucine, ornithine). Dynamic analysis further showed that placental type significantly influenced the postnatal metabolic reorganisation of valine and alanine. These preliminary observations require independent validation and should not be considered validated clinical biomarkers.