Objective: To study whether fetal main pulmonary artery (MPA) Doppler indices can predict the 
development of neonatal respiratory distress syndrome (RDS). Study Design: This Observational 
Prospective cohort study included pregnant women between 28- and 40-weeks gestation. The 
diagnostic accuracy of MPA Doppler measurements (pulsatility index (PI), resistance index (RI) and 
acceleration time/ejection time (At/Et)) for diagnosis of neonatal RDS was tested by comparing the 
Doppler findings with the clinical outcome. Results: Of the 40 eligible fetuses, 9 (22%) developed 
neonatal RDS There was a significant correlation between the AT/ET and the development of the 
RDS as the AT/ET was significantly lower in the RDS +ve group (mean 0.27) in comparison to the 
RDS -ve group (mean 0.34) (P 0.001). While both PI and RI showed no statistically significant 
difference in between the two groups. A cutoff value of 0.3 for At/Et predicted the development of 
RDS (sensitivity: 77.78%, specificity: 83.87%). Conclusion: Development of neonatal RDS can be 
predicted using the MPA At/Et with high sensitivity and specificity.