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

OBJECTIVE: The aim of this study was to determine whether sono-graphic 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 < .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.