Postnatally a rapid change occurs from a relatively hypoxic to a relatively hyperoxic environment, especially during artificial ventilation with all risks of ROS-formation. Among the non enzymatic antioxidative strategies the
vitamins E, C, A and B2 are of major importance.
Vitamin E is considered the most important radical scavenging
vitamin of the
lipid soluble compartment. Hereby
vitamin E itself is converted into a radical which is handed over to
vitamin C and
glutathione into the water soluble compartment. The
vitamin E content of the fetus increases with the fetal fat mass mainly during the last trimester of pregnancy. Placenta is only slightly permeable to
lipid soluble
vitamins.
Vitamin E deficiency may rapidly develop typically at about 6-8 weeks of age.
Vitamin E is able to prolong significantly the onset of retinopathic changes during
oxygen therapy and may prevent intraventricular
hemorrhage.
Vitamin C is together with
glutathione a major representative of the non enzymatic antioxidative system in the water soluble compartment. The best determinant of the
vitamin C status is its concentration in leukocytes.
Vitamin C reduces
iron to the divalent state which supports the
hydroxyl radical formation (Haber-Weiss reaction). This should be considered mainly in cases of intraventricular
hemorrhage.
Vitamin B2 acts mainly as cofactor of
glutathione reductase which keeps
glutathione in the reduced state. It can therefore be considered an indirect antioxidative
vitamin.
Vitamin B2 is destroyed by light.
Phototherapy has been recognized as a cause of
riboflavin deficiency.
Vitamin A comprises all retinols with properties like trans-
retinol.
Retinol storage in the fetal liver increases during late pregnancy. In both, premature and mature newborns, the serum concentrations amount to only about 50% of those of their mothers.
Vitamin A has a paramount importance for fetal lung development, because the individual
surfactant proteins are selectively regulated by
retinoic acid.