Fetal-maternal amino acid relationship in normal and intrauterine growth retarded (IUGR) pregnancies

Umbilical venous and maternal arterialized blood was obtained in 24 normal (AGA) and 31 intrauterine growth retarded (IUGR) pregnancies at the time of percutaneous umbilical blood sampling (PUBS). Sixteen AGA pregnancies were studied between 18 and 25 weeks gestation; 8 AGA and 31 IUGR pregnancies between 27 and 39 weeks gestation. No significant differences in both umbilical venous (UV), maternal arterial (MA), and fetal/maternal (F/M) ratio were observed for both total molar amino acid concentrations and the sum of the essential amino acids between the second and the third trimester. Fetal and maternal concentration of most amino acids was significantly correlated in both groups of AGA fetuses. IUGR fetuses presented significantly lower umbilical concentrations of the three essential branched chain amino acids, with a concomitant increase of maternal arterial concentrations when compared to normal fetuses of both gestational age groups. The F/M ratio of all essential amino acids was significantly reduced in IUGR pregnancies. The relationship between fetal and maternal values of the sum of the essential amino acids in IUGR pregnancies was significantly different from that observed in AGA pregnancies.