Abstract
Sixty-four samples of undialysed amniotic fluid were analysed in a free zone electrophoresis apparatus equipped with an ultra-violet (UV) scanning attachment for quantitative determinations of the protein concentrations. Total protein concentrations were measured by a biuret method. The electrophoretic patterns of amniotic fluid were generally simpler than those from maternal or cord serum or plasma. The albumin fraction showed the highest correlation to total protein levels in amniotic fluid both in normal pregnancies and in pregnancies complicated by haemolytic disease. Samples from pregnancies complicated by moderate to serious haemolytic disease showed a tendency to a more rapid decrease of the main protein fractions during the later phase of pregnancy. No significant connections could be found between the main protein fractions and cord blood haemoglobin or bilirubin concentrations. A probably significant correlation existed between the values for the albumin fraction and the values for amniotic fluid bile pigments (ΔE450) in normal pregnancies but not in pregnancies with haemolytic disease. A high nonprotein peak in the patterns from amniotic fluid was found to consist mainly of uric acid. The size of this peak was positively correlated with infant birth weight and negatively correlated with concentrations of albumin and total protein in normal pregnancies. Polyacrylamide gel gradient electrophoresis of some samples showed amniotic fluid to be rich in proteins with relatively low molecular weights.