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. 2008 Sep;25(8):473-80.
doi: 10.1055/s-0028-1085066. Epub 2008 Sep 4.

The probability of neonatal respiratory distress syndrome as a function of gestational age and lecithin/sphingomyelin ratio

Caryn St Clair  1 , Errol R Norwitz, Karlijn Woensdregt, Michael Cackovic, Julia A Shaw, Herbert Malkus, Richard A Ehrenkranz, Jessica L Illuzzi
Affiliations

The probability of neonatal respiratory distress syndrome as a function of gestational age and lecithin/sphingomyelin ratio

Caryn St Clair et al. Am J Perinatol. 2008 Sep.

Abstract

We sought to define the risk of neonatal respiratory distress syndrome (RDS) as a function of both lecithin/sphingomyelin (L/S) ratio and gestational age. Amniotic fluid L/S ratio data were collected from consecutive women undergoing amniocentesis for fetal lung maturity at Yale-New Haven Hospital from January 1998 to December 2004. Women were included in the study if they delivered a live-born, singleton, nonanomalous infant within 72 hours of amniocentesis. The probability of RDS was modeled using multivariate logistic regression with L/S ratio and gestational age as predictors. A total of 210 mother-neonate pairs (8 RDS, 202 non-RDS) met criteria for analysis. Both gestational age and L/S ratio were independent predictors of RDS. A probability of RDS of 3% or less was noted at an L/S ratio cutoff of > or = 3.4 at 34 weeks, > or = 2.6 at 36 weeks, > or = 1.6 at 38 weeks, and > or = 1.2 at term. Under 34 weeks of gestation, the prevalence of RDS was so high that a probability of 3% or less was not observed by this model. These data describe a means of stratifying the probability of neonatal RDS using both gestational age and the L/S ratio and may aid in clinical decision making concerning the timing of delivery.

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Figures

Figure 1
Figure 1
The method of subject selection resulting in the study population is shown. NICU, neonatal intensive care unit; PPHN, persistent pulmonary hypertension; RDS, respiratory distress syndrome; TTN, transient tachypnea of the newborn; YNHH, Yale-New Haven Hospital.
Figure 2
Figure 2
Gestational age distribution of the patient population. Data represents gestational age at amniocentesis; all lecithin/sphingomyelin ratio values included in the final analysis were obtained within 72 hours of delivery. Absolute patient numbers are included above each bar.
Figure 3
Figure 3
Risk of neonatal respiratory distress syndrome (RDS) as a function of gestational age. Data are shown for the current population and from two prior publications showing the change in prevalence of RDS over time between 32 and 38 weeks likely due to the introduction of antenatal corticosteroids: Usher et al from 1957–1963 (prior to the introduction of antenatal steroids) and Robertson et al from 1983–1986 (where ~;40% of subjects received antenatal steroids).
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