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Trace elements
ОглавлениеHeavy metals can accumulate in AF, yet their potential impact on the developing fetus is not well understood.356 The topic was reviewed by Caserta et al.,357 who describe their particular concerns with toxicity of lead, mercury, and cadmium on intrauterine growth and neurologic damage. AF copper and zinc are among the trace elements that have stable levels during the second and third trimesters.358, 359 No direct correlation has yet been made in AF studies between central nervous system development or enzymatic reactions and variations in trace element levels in humans. However, zinc deficiency is thought to potentiate the teratogenic effect of alcohol in the fetal alcohol syndrome.360
Further to those observations and another by Chez et al.358 on copper and zinc, Hall et al.343 added proton‐induced X‐ray emission (PIXE) and direct plasma‐atomic emission spectrometry (DCP‐AES) for multi‐element analysis. Their studies were carried out on 90 AF samples obtained between 16 and 19 weeks of gestation from women referred for advanced maternal age (Table 3.3).
Table 3.3 Trace elements in amniotic fluid (see also Table 3.5)
| Element (Z) | N | Mean | SD |
|---|---|---|---|
| B (5) | 88 | 32.2 | 1.7 |
| Mg (12) | 200 | 16.0 a,b | 3.1 |
| Al (13) | 200 | 424.1 | 1.2 |
| Si (14) | 200 | 247.2 | 2.7 |
| P (15) | 200 | 28.3 a,b | 4.0 |
| K (19) | 200 | 148.4 b | 1.1 |
| Ca (20) | 200 | 73.2 a, b | 12.2 |
| Ti (22) | 200 | 13.2 | 2.0 |
| V (23) | 200 | 183.1 | 1.4 |
| Cr (24) | 200 | 4.9 | 1.9 |
| Mn (25) | 200 | 4.7 | 1.8 |
| Fe (26) | 200 | 3475.8 | 14.5 |
| Co (27) | 88 | 44.0 | 1.8 |
| Ni (28) | 200 | 24.0 | 2.2 |
| Cu (29) | 200 | 1437.0 b | 35.3 |
| Zn (30) | 88 | 216.5 | 15.1 |
| Rb (37) | 200 | 217.4 | 80.1 |
| Sr (38) | 200 | 21.2 a | 7.1 |
| Ag (47) | 88 | 15.1 a | 7.8 |
| Sn (50) | 88 | 95.6 | 1.5 |
| Ba (56) | 200 | 17.0 | 6.0 |
| Pb (82) | 88 | 116.7 | 1.4 |
Source: Hall et al. 1983343 (see also Dawson et al. 1999228).
a Concentration mg/mL.
b Arithmetic mean.
Mean gestational age, 17.1 weeks. All concentrations are ng/mL except where noted.
Copper, zinc, bromine, lead, and rubidium assays show no significant differences among groups of normal, hypotrophic, and trisomic fetuses.288 Bussière et al.230 stressed that the wide dispersion of reported metal concentration values in AF may be secondary to sample variability, lack of technical uniformity, and the presence of contaminants. Nevertheless, results obtained for those trace elements are of the same order of magnitude as in previously published reports.343, 361 Both AF vitamin A and zinc levels were elevated in the presence of a fetal NTD.362, 363
Tamura and co‐workers364 studied the relationships between AF and maternal blood nutrient concentrations. Folate, zinc, copper, and iron concentrations in AF were significantly lower than plasma levels; this relationship was reversed for vitamin B12. No correlation was found between AF and blood nutrient concentrations and pregnancy outcome. Vitamin B12 concentrations are lower in AF in the presence of fetal NTDs compared with unaffected fetuses.365, 366
Luglie and co‐workers367 studied the total concentration of mercury (Hg) in AF and found no direct relationship with the number of occlusal extension of fillings using dental amalgam. Mercury is one of the components of dental amalgam that can pass into the organs and biologic fluids. A study of pregnancies to mothers in a region of Poland with high levels of mercury pollution confirmed high levels of Hg in most of the newborn cord blood samples, but no statistically significant correlation was identified between Hg levels and delivery week, APGAR score, or placenta or newborn weight.368
Milnerowicz et al.369 suggested that smoking may have an impact on uterine blood vessels and may cause placental vascular insufficiency and changes in fetal membranes. In this study, the concentration of Zn and Cd were half the value and Pb 10 times lower in AF from a small number of women as compared with a normal pregnancy. Cotinine and Cd were much higher in women with oligohydramnios who were also heavy smokers.
