SM	N-Palmitoyl-D-erythro-sphingosylphosphorylcholine
DPPC	1,2-dipalmitoyl-sn-glycero-3-phosphocholine
nRDS	Neonatal respiratory distress syndrome
PCR	Principal component regression
PLSR	Partial least squares regression
L/S	Lecithin/sphingomyelin ratio
ATR–FTIR	Attenuated total reflectance–Fourier transform infrared spectrometry
MSE	Mean squared error
R 2	Coefficient of determination
RMSE	Root mean squared error
PI	Prediction interval
PCs	Principal components (model factors for principal components regression)
LVs	Latent variables (model factors for partial least squares regression)
AF	Amniotic fluid
BAL	Bronchoalveolar lavage
GA	Gastric aspirate