Influence of maternal factors on cord and neonatal plasma micronutrient levels.

The influence of gestational length, maternal prenatal supplement and maternal levels on umbilical cord and neonatal plasma selenium, alpha-tocopherol, and retinol were studied and appropriate reference intervals for ongoing studies of gestational and perinatal micronutrient requirements were derived. We measured retinol, alpha-tocopherol (total and alpha-tocopherol:cholesterol ratio), selenium, and glutathione peroxidase in 160 umbilical cord samples and 58 paired maternal and neonatal samples collected on the third postpartum day. Selenium and glutathione peroxidase were also measured in 25 paired umbilical artery and vein samples. The strongest correlation with gestational age and birthweight was found for the cord blood variables, whereas levels in maternal blood were not related to either gestation or weight. Neonatal values were significantly lower than maternal for selenium (0.96 [0.25] compared with 1.56 [0.27] mumol/liter), retinol (0.54 [0.19] and 1.26 [0.45] mumol/liter), alpha-tocopherol (11.5 [3.63] and 32.4 [9.20] mumol/liter), and glutathione peroxidase (446 [174] and 873 [176] U/liter) but not for the ratio of alpha-tocopherol:cholesterol (5.0 compared with 6.0). Maternal use of tocopherol and retinol supplements did not significantly affect blood concentrations. Maternal plasma selenium levels at term were about 60% of nonpregnant adult females. Selenium concentration and glutathione peroxidase activity did not differ between paired umbilical cord arterial and venous samples. Selenium, retinol, and glutathione peroxidase differed between infants born before or after 37 weeks' gestation.