Acceleration/ejection time ratio in the fetal pulmonary artery predicts fetal lung maturity.

OBJECTIVE The aim of this study was to determine whether sonographic fetal pulmonary artery flow velocity waveforms correlate with amniotic fluid biomarkers of fetal lung maturity. STUDY DESIGN We studied women with singleton pregnancies undergoing clinically indicated amniocentesis for fetal lung maturity at Yale-New Haven Hospital. Fetal pulmonary artery flow velocity measurements, including systolic/diastolic ratio, pulsatility index, resistance index, and acceleration-time/ejection-time ratio were obtained using spectral Doppler ultrasound. Pearson's correlation coefficient was used to determine the association between fetal pulmonary artery flow velocity parameters and the lecithin/sphingomyelin ratio. RESULTS Twenty-nine subjects met study criteria. The acceleration-time/ejection-time ratio was inversely correlated with the lecithin/sphingomyelin ratio (r = -0.76; P < or = .001). This relationship was maintained after controlling for potential confounders. Other fetal pulmonary artery flow velocity measurements were not associated with the lecithin/sphingomyelin ratio. CONCLUSION There is an inverse correlation between the acceleration-time/ejection-time ratio in the fetal pulmonary artery and the amniotic fluid lecithin/sphingomyelin ratio. This suggests that ultrasound evaluation of fetal pulmonary artery blood flow may be a promising new noninvasive technique to evaluate fetal lung maturity.