The role of doppler waveforms in the fetal main pulmonary artery in the prediction of neonatal respiratory distress syndrome

OBJECTIVE: To describe changes in the Doppler waveforms of the fetal main pulmonary artery (MPA) throughout gestation and to assess their predictive value of neonatal respiratory distress syndrome (RDS). STUDY DESIGN: In the first phase of this study, we performed Doppler measurement of MPA acceleration time (AT), ejection time (ET), peak systolic velocity, end-diastolic velocity, mean velocity, pulsatility index, and resistance index in 288 healthy fetuses. In the second phase, we carried out these measurements in a prospective cohort of 52 pregnant women with impending preterm birth. RESULTS: In phase I, satisfactory fetal MPA Doppler recordings were collected in 284 of 288 (98.6%) normal fetuses. Significant and positive linear correlations were found between gestational age and AT, AT/ET ratio, peak systolic velocity, and mean velocity (p < 0.01), with the strongest correlations concerning AT (r = 0.898) and AT/ET ratio (r = 0.868). In phase II, satisfactory fetal MPA Doppler waveforms were obtained in 43 of 44 (97.7%) fetuses. Of these, 14 (32.6%) developed RDS and 29 did not. Using less than or equal to the fifth percentile as a gestational age-specific cutoff, AT alone could predict RDS with a sensitivity of 78.6% and a specificity of 89.7%. The AT/ET ratio could predict RDS with 71.4% sensitivity and 93.1% specificity. CONCLUSIONS: Fetal MPA Doppler velocimetry can reliably be obtained throughout gestation. AT and AT/ET ratios of the fetal MPA Doppler waveform may help identifying fetuses at risk of developing neonatal RDS.