Consequences of methemoglobinemia in pregnancy in newborns, children, and adults: issues raised by new findings on methemoglobin catabolism.

Objective: The aim of this review is to warn about the effects of methemoglobin and its catabolic products and the toxic effects caused by environmental oxidants that cause high-risk pregnancy and may later impair the health of newborns, children and adolescents.
Methods: In our study of pregnant women (n = 36) whose methemoglobin level was >1.5 g/l, we took blood samples from their newborns to determine the frequency of sister chromatid exchange (SCE) by cultivating lymphocytes. The research took place at the Department of Biology and Medical Genetics of the School of Medicine in Rijeka (Croatia).
Results: The results have shown that no deviation in the SCE frequency was found in either case (1990). We examined data on the health of newborns collected at perinatal hospital departments in Rijeka (Croatia), the preschool office and school service at the Labin Health Center and continued until they were 18 years of age (2008). The statistics obtained by applying the chi-square test show that the incidences of neonatal jaundice (p = 0.034), heart murmur at a later age (p = 0.011) and dyslalia and learning/memory impairments (p = 0.002) were significantly higher than in children of control mothers (n = 19).
Conclusion: Depending on the mother's exposure to environmental oxidants, during its development the fetus is more likely to be affected by methemoglobin and hemolysis. Oxidants affect the vascular endothelium of kidneys, brain and other vital organs, because they have the capacity to cross the damaged fetomaternal placental barrier. 'Fetal preeclampsia' is an expected manifestation of the condition. Our research proves our thesis on the pathophysiological relationship between methemoglobinemia and unexplained jaundice and hyperbilirubinemia, heart murmur at a later age, dyslalia and learning and memory impairments that have not exactly been demonstrated yet.