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.