[Thermolabile fraction of amniotic alkaline phosphatase and fetal lung maturity]

In order to predict respiratory distress syndrome (RDS) in the newborn due to the lack of surfactant, we measured the change in the total and heat labile fraction of alkaline phosphatase (ALP) in amniotic fluid obtained at various gestational ages. Heat labile alkaline phosphatase increased both absolutely and in relation to total ALP from 32 weeks to term. We have used the ratio heat labile ALP/total ALP to predict lung maturity. There was no respiratory distress in infants born after the heat labile ALP/total ALP in the amniotic fluid was above 0.7. The assay is technically easy so that measurement of this ratio should help predict which infant will develop RDS.