Fluorescence polarization in gastric aspirate and in amniotic fluid and its relationship to the respiratory distress syndrome.

Fluorescence polarization of diphenylhexatriene (DPH), added to amniotic fluid can be used to estimate fetal lung maturity. In this study we estimated the fluorescence polarization (FP) value of gastric aspirates of newborns and of amniotic fluids and studied the relationship between the FP value and neonatal lung function. Gastric aspirates of 51 newborns and amniotic fluids of 13 cases were mixed with a DPH-phosphate buffered saline solution and incubated for 30 minutes at 37 degrees C. Fluorescence polarization was measured at 22 degrees C. The FP values of amniotic fluid are in accordance with results previously found. A highly significant negative correlation was present between the FP value in amniotic fluid and gestational age. The highest FP values were found in amniotic fluids of infants in whom respiratory distress developed. The FP values of gastric aspirates decreased also with gestational age. A rather poor negative correlation, however, was found between these FP values and gestational age. We also noticed that, before the 36th week of gestation, the FP values in gastric aspirates tend to be lower than those in amniotic fluids. Both high and low FP values were estimated in gastric aspirates of infants with RDS and of infants without respiratory problems. These results show that the measurement of the FP value in gastric aspirates of newborns is not an useful method to determine whether the infant will develop RDS or not.