Fetal lung maturity.

Respiratory distress syndrome of the newborn infant caused by immaturity of the fetal lung continues to be a clinical problem. Measurement of pulmonary surfactant production is the most effective way to evaluate pulmonary maturity. Since the first fetal lung maturity test was described more than two decades ago, advances in methodology have produced diagnostically sensitive tests that are both rapid and precise. Unfortunately, currently available tests continue to demonstrate low diagnostic specificity and remain poor predictors of fetal lung immaturity. We review the background, methodology, pre-analytical and analytical concerns, and clinical performance of various fetal lung maturity assays, and discuss the appropriate use and interpretation of these tests.