Immature lecithin/sphingomyelin ratios and neonatal respiratory course.

ABSTRACT

OBJECTIVE: We hypothesized that the absolute value of an immature lecithin/sphingomyelin ratio, in addition to gestational age and birth weight, contributes significantly to predicting the clinical course of the neonate. The lecithin/sphingomyelin value may therefore enhance clinical decision-making regarding timing of delivery and use of tocolytics in high-risk pregnancies. STUDY DESIGN: One hundred four mother-baby pairs with delivery within 72 hours of an immature lecithin/sphingomyelin determination in the 3-year period immediately before the initiation of surfactant therapy in our hospital were retrospectively reviewed. Stepwise regression was performed for the independent variables of gestational age, birth weight, and lecithin/sphingomyelin values in a linear model to predict total days of respiratory support (oxygen, continuous positive airway pressure, or mechanical ventilation). RESULTS: In the patients without preterm premature rupture of membranes the lecithin/sphingomyelin value was the best predictor of duration of respiratory support (R2 = 0.2426, F = 12.4908, p = 0.011). After gestational age was controlled for, there was a significant inverse correlation between the lecithin/sphingomyelin value and days of respiratory support (F = 4.634, p = 0.031). In the patients with preterm premature rupture of membranes with vaginally collected fluid, however, lecithin/sphingomyelin values did not contribute significantly in predicting duration of respiratory support. Rupture-to-delivery interval and gestational age were the best predictors in this group. CONCLUSION: Although a mature lung profile is the ideal situation, preterm delivery may be indicated in pregnancies complicated by maternal disease or evidence of possible fetal compromise. We conclude that in patients without premature rupture of membranes the absolute value of the immature lecithin/sphingomyelin ratio is a better predictor than gestational age or birth weight of duration of respiratory support and should be considered in timing of delivery.