Amniotic fluid analysis and foetal erythroblastosis

Determination of bilirubin in amniotic fluid: a comparison of some current methods

Three methods for the estimation of bilirubin in amniotic fluid are compared. The within-batch precision and recovery of bilirubin by each method has been studied, and the effects of the presence of haemoglobin, methaemoglobin, and methaemalbumin in varying concentrations have been investigated. Measurements on amniotic fluid from patients with rhesus isioimmunization have also been compared and regression equations calculated. The results of the three methods agree reasonably well so long as no haemoglobin degradation products are present. It is suggested that in the presence of these products a method involving organic solvent extraction of bilirubin gives the most accurate result.

Liquor bilirubin levels in normal pregnancy: a reassessment of early prediction of haemolytic disease

A comparison was made between chemically and spectrophotometrically determined concentrations of total bile pigment in the liquor amnii. For the period 16 to 26 weeks' gestation the upper limit of normal bile pigment to protein ratio was found to be 0.4. Levels above this would be required as an indication for intrauterine transfusion. In 110 cases of isoimmunization of pregnancy these criteria were applied in the diagnosis of severity of the condition. The ratio of the bile pigment to protein was used rather than a simple bile pigment measurement, and found to be valuable.Nevertheless, it is important to emphasize that fallacious high bilirubin readings may arise by using whatever method, particularly owing to bilirubin and other breakdown products of blood contaminating the liquor.