INTRAUTERINE ELIMINATION OF PYRIDOXAL 5'-PHOSPHATE IN FULL-TERM AND PRETERM INFANTS

This study addressed the intrauterine elimination of pyridoxal 5'-phos phate (PLP) in 15 preterm and 31 fullterm infants, thereby providing e stimates of fetal vitamin consumption as well as maternal vitamin requ irements during pregnancy. Elimination was calculated as the differenc e in the plasma PLP concentration between umbilical vein and umbilical artery times the umbilical plasma flow. Plasma flow in the umbilical vein was calculated from pulsed Doppler ultrasonographic determination of blood flow and from the hematocrit value. Plasma PLP concentration s were assayed in maternal and umbilical veins and the umbilical arter y; PLP concentrations were similar in preterm and full-term infants (P > 0.05). In both groups of infants the PLP concentration in the umbil ical vein (preterm: 100.3 nmol/L; full-term: 63.9 nmol/L) was ninefold higher than in maternal circulation (P < 0.001). In full-term infants , PLP concentrations in maternal and umbilical veins correlated weakly (r = 0.358, P < 0.05), but no significant correlation was found in th e preterm group (P > 0.05). The arteriovenous concentration gradient o f PLP in cord vessels was higher in preterm infants (15.0 nmol/L) than in full-term infants (2.1 nmol/L), but the difference between groups was not significant (P > 0.05). Preterm infants eliminated 1.7 nmol PL P . kg(-1) . min(-1) in utero, whereas full-term infants eliminated 0. 2 nmol PLP . kg(-1) . min(-1) (P < 0.05). The significantly higher pla sma flow in preterm infants (116 mL . min(-1) . kg(-1)) compared with full-term infants (78 mL . min(-1) . kg(-1)) contributed to the higher PLP elimination in preterm infants.