Prevalence and etiology of respiratory distress in infants of diabetic mothers: predictive value of fetal lung maturation tests.

The purpose of this study was to investigate the prevalence of respiratory distress syndrome attributable to surfactant deficiency in infants of diabetic mothers tested for fetal lung maturation. Three tests were assessed: (1) lecithin/sphingomyelin ratio, (2) phosphatidylglycerol concentration, and (3) optical density at 650 nm. From January 1987 through June 1989, 526 diabetic gestations were delivered within 5 days of fetal lung maturation testing. Surfactant-deficient respiratory distress syndrome was present in five infants (0.95%); all were less than 34 weeks' gestational age. Other causes of respiratory distress were transient tachypnea of the newborn (n = 5), hypertrophic cardiomyopathy (n = 4), pneumonia (n = 2), polycythemia (n = 1), and meconium aspiration syndrome (n = 1). The use of standard maturity values of lecithin/sphingomyelin ratio greater than or equal to 2.0, phosphatidylglycerol greater than 2% to 5%, and optical density at 650 nm greater than or equal to 0.150 were evaluated. Each test had a 100% sensitivity in identifying surfactant-deficient respiratory distress syndrome and a 100% negative predictive value in identifying the absence of disease. All three tests had a low positive predictive value: 15% for lecithin/sphingomyelin ratio, 9% for phosphatidylglycerol, and 3% for optical density at 650 nm. We concluded that most cases of respiratory distress in the infants of diabetic mothers were unrelated to surfactant deficiency. The standard maturity values used in fetal lung maturation tests were valid in the diabetic gestation. The optical density at 650 nm was useful as a first-line test to predict the absence of surfactant-deficient respiratory distress syndrome.