Objective: The purpose of this study was to determine whether the pulsatility index (PI) of the ductus arteriosus could predict the occurrence of pulmonary hypoplasia secondary to congenital disorders or complications during pregnancy. Sample and Methods: In this longitudinal study, 78 uncomplicated pregnancies and 43 pregnancies complicated by various disorders or complications with regard to pulmonary hypoplasia were studied by Doppler sonography between 18 and 35 weeks of gestation. A PI >97.5th percentile was considered abnormal. Results: Using a multilevel modelling, the reference curve of the PI of the ductus arteriosus was created based on 301 measurements. Of the 43 complicated pregnancies, 21 infants (49%) were diagnosed with pulmonary hypoplasia on postmortem examination and/or the clinical and radiological presentation. Using the PI, a sensitivity of 38%, a specificity of 95%, a positive predictive value of 89% and a negative predictive value of 62% were found. Conclusion: The PI of the ductus arteriosus is not useful in predicting the occurrence of pulmonary hypoplasia secondary to congenital disorders or complications during pregnancy. © 2009 S. Karger AG, Basel.