Evaluation of amniotic fluid zinc levels in open neural tube defects

Summary Amniotic fluid zinc concentration (mean 1·6±0·5μmol/L) in 131 pregnancies without fetal abnormalities in the second trimester did not increase with gestation. An elevated mean zinc level, 6·8±2·5 μmol/L, was detected in seven amniotic fluids with anencephalic fetuses. In amniotic fluids from 20 cases of fetal open spina bifida, a mean zinc concentration of 2·8±1.5 μmol/L was also significantly elevated but there was only elevation (>2 s.d.) in 40 per cent of these 20 cases of open spina bifida. Amniotic fluid zinc measurements are not suitable to complement α-fetoprotein estimations for the detection of open neural defects. There were no normal fetuses with elevated zinc amniotic fluid concentrations but in 6 out of 8 with fetal malformations other than neural tube defects, amniotic fluid zinc values were raised. Contamination with maternal blood resulted in falsely elevated zinc concentrations in 52 per cent of contaminated amniotic fluids.