Surface properties of amniotic fluid and fetal lung maturity.

Surface activity of 75 amniotic fluid samples from pregnancies which ended before term or at term with small-for-date newborns was measured in the surface balance. The results were correlated with the clinical symptomatology and the birth weight of the newborn. The surface properties of the lungs of those infants who had died were assessed by the buble stability method (Pattle), by recording of pressure-volume diagram and by measurements of surface activity of lung extracts. The results indicate that gamma-min is the essential parameter in determining the degree of fetal lung maturity. In cases with gamma-min values of amniotic fluid above 27 dyn/cm, a 100% respiratory distress syndrome (RDS) incidence is to be expected; values between 23 and 27 dyn/cm have a 70% values between 17 and 23 dyn/cm have a 30% incidence of RDS and in all cases with values below 17 dyn/cm, RDS may be rules out. When induced delivery before term is considered, this method of determining the degree of fetal lung maturity is, therefore, of significant prognostic reliability.