New data on toxic metal intoxication (Cd, Pb, and Hg in particular) and Mg status during pregnancy.
The technological revolution we witness today poses a threat to the homo sapiens species, and its biological results are unpredictable. Excess toxic metals in the environment and the deficiency of bio-elements are particularly harmful for developing organisms. Long-term fetal exposure during pregnancy to even lower concentrations of toxic metals, which have the ability to accumulate, often leads to irreversible developmental disorders, On the basis of accessible literature, the paper presents transplacental transmission of cadmium, lead and mercury to the fetus. The disadvantageous effects of cadmium and lead on ionic transmission, functional potential and submicroscopic amnion structure as well as the interdependence between the unfavorable effects of these two metals on the amniotic membrane and the competitive antagonistic activity of Mg ions are emphasized. This paper presents a hypothesis suggesting the involvement of cadmium in the etiopathogenesis of eclampsia based on the literature. It also considers the present state of knowledge of the toxic effects of Cd, Pb and Hg on the course of pregnancy and fetal development. Magnesium--an intracellular cation second in importance to potassium plays a significant biological role, though it has not been fully explored yet. The concentration of Mg in the placental and fetal tissues increases during pregnancy. The requirements for this element in a pregnant woman's organism generally exceed its supply; hence, pregnancy should be considered a condition of 'physiological hypomagnesemia'. The accessible data concerning the content of Mg during pregnancy in the blood as well as in the uterine muscular wall in physiological and pathological pregnancies are diverse. The prevailing opinion is that oral supplementation of magnesium during pregnancy makes up for its deficit in the organism of the pregnant woman and also positively influences fetal development. It is recommended to administer magnesium with food in the form of magnesium salts at the dose 5 mg/kg body mass daily. In clinical obstetric practice magnesium therapy is necessary in cases of imminent preterm birth and preeclampsia. This paper discusses the mechanism and therapeutic effectiveness of magnesium sulfate as used in complications of pregnancy. The contamination of the pregnant woman's organism by toxic metals--cadmium, lead and mercury--poses a serious risk of the same quantitative degree of contaminating the organism of the child developing in her womb. Qualitative changes may be much more serious in the fetus as they affect young structures, intensively developing, with no well-formed defense mechanisms. It is also worth mentioning that the complications in the course of pregnancy may result from toxic metal concentrations lower than those leading to fetal necrosis or premature termination of pregnancy.
Clinic of Obstetrics and Pathology of Pregnancy, Medical University, 16 Staszica St., 20-081 Lublin, Poland.
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Semczuk
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Semczuk-Sikora
D005260:Female; D000075322:Heavy Metal Poisoning; D006801:Humans; D008274:Magnesium / Q000008:administration & dosage / Q000378:metabolism*; D011247:Pregnancy
D008274:Magnesium