Relationship between fetal pulmonary artery blood flow velocity waveform and fetal lung length in pregnancies complicated by oligohydramnios

Abstract

Objectives: The objective of this study is to evaluate weather there is a correlation between Doppler velocity waveform parameters obtained from fetal pulmonary artery and fetal lung length considered as one of the lung hypoplasia risk parameters in pregnancies complicated by oligohydramnios.Methods: A total of 35 singleton pregnancies between 26 and 39 weeks complicated by oligohydramnios due to premature rupture of the membranes, placental insufficiency or idiopathic etiology and 69 normal pregnancies were examined by real time ultrasonography, color and pulse Doppler. Pulse Doppler signal was obtained from the distal part of right or left pulmonary artery after visualization with color Doppler at the level of four chamber view. The systolic to diastolic ratio, resistance index and pulsatility index were used to quantify velocity waveforms. The right lung of the fetus was measured longitudinally from the apex next to clavicle to the base at the top of diaphragm. The results of fetal lung length measurements were compared with namogram given by Roberts.Results: Statistically significant difference in distal pulmonary artery pulsatility index between normal pregnancies (1.74 ± 0.23) and pregnancies complicated by oligohydramnios (2.72 ± 0.56) with decreased value of fetal lung length (below fifth percentile) was observed. The sensitivity, specificity, positive and negative predictive value of 95, 91, 93, 91%, respectively, were obtained. In the group with oligohydramnios and normal values of fetal lung length, the difference in pulsatility index in comparison with normal pregnancies was not significant. No differences in systolic to diastolic ratio and resistance index between examined groups were found.Conclusions: Strong relationship between increased pulsatility index value obtained from distal part of pulmonary artery and decreased value of fetal lung length measurement in pregnancies complicated by oligohydramnios was observed. The measurement of pulmonary artery pulsatility index enriched with fetal lung length may give additional information useful in predicting pulmonary hypoplasia risk.