Neonatal respiratory distress syndrome as a function of gestational age and an assay for surfactant-to-albumin ratio

OBJECTIVE: Neonatal respiratory distress syndrome (RDS) affects approximately 1% of live births, and the probability of RDS continues to be a major determinant in the timing of delivery. This study was designed to investigate the optimal gestational age-specific cutoff value for a surfactant-to-albumin ratio assay for predicting RDS. METHODS: Amniotic fluid surfactant-to-albumin ratio data were collected prospectively for a 2-year period. Women were included in the study if they delivered within 72 hours of surfactant-to-albumin ratio estimation. RDS was defined by the presence of 2 or more of the following criteria: evidence of respiratory compromise shortly after delivery and a persistent oxygen requirement for more than 24 hours, administration of exogenous pulmonary surfactant, and/or radiographic evidence of hyaline membrane disease. RESULTS: A total of 415 mother-neonate pairs (28 RDS, 387 non-RDS) met criteria for analysis. Both gestational age and surfactant-to-albumin ratio values were independent predictors of RDS. By modeling the odds of RDS by using a logistic regression with gestational age and surfactant-to-albumin ratio values as continuous variables, a probability of RDS of 15% or less can be achieved with a surfactant-to-albumin ratio cutoff of 60 mg or more surfactant/g albumin at 28 weeks of gestation, 50 or more at 30 weeks, 40 or more at 33 weeks, 30 or more at 35 weeks, and 20 or more at 37 weeks. CONCLUSIONS: These data describe a means of stratifying the probability of neonatal RDS using both gestational age and surfactant-to-albumin ratio value and may be a useful model for clinical decision-making. (C) 2004 by The American College of Obstetricians and Gynecologists.