Effect of blood in amniotic fluid on the detection of phosphatidylglycerol

Samples of amniotic fluid were mixed with serum or red blood cells (RBC) in order to determine the effect of blood contamination on the detection of phosphatidylglycerol (PG). Samples of amniotic fluid were obtained from patients in the second trimester of pregnancy and at term. PG standard was added to half of the aliquots of the second-trimester fluid. The samples of fluid were tested before and after the addition of maternal or fetal serum or RBC in concentrations up to 20%. Two-dimensional thin-layer chromatographic procedures were performed to determine the presence or absence of PG. The results obtained showed that serum or RBC contamination of amniotic fluid without PG did not result in the appearance of a PG spot on the chromatographic plate. Neither serum nor RBC contamination interfered with the detection of PG in those fluids in which it was present. Maternal and fetal blood were similar in their failure to affect the detection of PG. These data suggest that PG determination for fetal lung maturity is a reliable test in the presence of bloody amniotic fluid.