Importance of simultaneous determination of coproporphyrin and hemoglobin in contaminated amniotic fluid

To detect the presence of meconium and blood, we determined coproporphyrin and hemoglobin in 78 amniotic fluid samples, classified according to their visual aspect as clear (n = 45) or meconium-stained (n = 33). Among the 33 samples visually judged as meconial, a comparison of the results of their biochemical analysis with the mean values for clear amniotic fluids showed that only five of the 33 were contaminated solely with meconium. Seven others were exclusively bloody, and 19 were meconial and bloody. In two, the contaminant was neither meconium nor blood. Evidently, when the fluid is brownish, simple visual examination does not suffice for distinguishing meconium from old blood or other pigments. We propose a simple, rapid, and reliable method for simultaneously measuring contamination with meconium or blood.