PREDICTION OF NEONATAL RESPIRATORY DISTRESS BY ESTIMATION OF AMNIOTIC-FLUID LECITHIN

Abstract

A simple chemical method for estimating the total lipid, phospholipid, and lecithin content of amniotic fluid is described. It has been used to test the hypothesis that neonatal respiratory function is related to the pre-delivery levels of these substances in amniotic fluid. 171 samples of amniotic fluid taken at different stages of pregnancy from 156 patients were assayed; 110 samples were obtained in the 24 hours before delivery of the infant. Amniotic-fluid lecithin levels of around 3·5 mg. per 100 ml. would seem to be critical, for pre-delivery levels above this value were in every case associated with normal respiratory function, even in 12 infants who were "small for dates " or premature. By contrast the pre-delivery amniotic-fluid lecithin concentration was below 3·5 mg. per 100 ml. (range 0·6-3·4 mg. per 100 ml.) in 12 out of 13 infants who developed respiratory-distress syndrome. The lecithin concentration in the amniotic fluid seems to be a sensitive index of fetal lung maturity and of the potential risk of respiratory distress developing in the baby.