Additional file 1: Supplementary Fig. 1 Relative abundances of amino acids in maternal and fetal plasma (a,b) and placental fluids (c,d). Amino acids in plasma are expressed as concentrations (nmol/mL), and amino acids in placental fluids are expressed as total amounts (concentration × volume). Glutamate, glycine, and alanine were most abundant in maternal plasma (a), while glutamate, serine, glycine, and alanine were most abundant in fetal plasma (b). All amino acids, except for arginine and citrulline, were more abundant in fetal plasma than maternal plasma. The most abundant amino acids in allantoic fluid were serine and taurine (c). The most abundant amino acids in amniotic fluid were asparagine and serine (d).