Use of quantitative amniotic fluid phosphatidylglycerol as a criterion for fetal lung maturation

Phosphatidylglycerol (PG) in amniotic fluid was quantitatively measured by thin-layer chromatography (TLC) in 941 amniotic fluid samples and related to the presence or absence of respiratory distress syndrome (RDS) in neonates born within 7 days of the amniocentesis. In 639 case tests with PG 1 nmol/ml or more of amniotic fluid, there was no RDS. However, there were six cases of RDS associated with 109 tests of PG from 0 to less than 1 nmol/ml. These 109 tests would all have been reported as PG positive if PG were only qualitatively assessed on the TLC plate by the naked eye. The highest incidence of RDS occurred when PG was absent (23 RDS of 193 patients). Hence, this study suggests that quantitative analysis of PG determines a cutoff point of PG that eliminates false-positive PG assessments (1 nmol/ml in our laboratory). There was no difference in the levels of PG between males and females at equal gestational ages, but the incidence of RDS among male neonates was 2.4 times higher (p less than 0.05) than female neonates in the group with an immature amniotic fluid lecithin to sphingomyelin ratio and PG less than 1.0 nmol/ml.