The intrauterine turnover of thiamin in preterm and full-term infants.

In thirteen preterm infants, 45 full-term infants, and their mothers thiamin was analyzed in plasma from maternal veins, umbilical arteries, umbilical veins, and placental tissue. The blood flow in the umbilical veins was determined by pulsed Doppler ultrasonography. Thiamin-dependent transketolase was measured in erythrocytes from full-term infants and their mothers. Plasma thiamin concentrations in umbilical veins from preterm infants (227.0 +/- 85.0 nmol/L) and full-term infants (121.3 +/- 103.3 nmol/L) were seven times greater than maternal concentrations (p < 0.005). Maternal and umbilical thiamin concentrations were lower in the full-term group compared to the preterm group (p < 0.05). Arteriovenous concentration gradients were not feasible. The blood flow in the umbilical veins was higher in full-term compared to preterm infants (p < 0.05). However, intrauterine thiamin supply (plasma thiamin concentration times umbilical plasma flow) and placental thiamin concentrations were not different between preterm and full-term infants. Thiamin saturation of transketolase was greater in fetal than in maternal erythrocytes (p < 0.005); severe thiamin deficiency was not observed. Our findings suggest that thiamin turnover is similar in early and late pregnancy. Fetal tissue uptake of thiamin is not substantial. Transketolase activities suggest that thiamin status is sufficient even in late pregnancy.