To explore the characteristics of branch pulmonary artery flow patterns in fetuses with left heart hypoplasia syndrome (HLHS).

HLHS fetuses were divided into an unobstructed group and an obstructed group according to the blood flow pattern across the interatrial septum. Main pulmonary artery diameter, right pulmonary artery diameter, and Doppler parameters of first-order right pulmonary artery of both groups were measured by fetal echocardiography and compared with those of normal controls.

There was a significant difference in the diameter of pulmonary trunk among different the three groups (F=198.56, P<0.05), and the main pulmonary artery diameter in the two groups of HLHS fetuses were larger than that in normal controls (t=-18.501, -13.97, P<0.05), but there was no significant difference between the two groups of HLHS fetuses (P=0.85). There was no significant difference in right pulmonary artery diameter among the three groups (P=0.59). The end-diastolic velocity, time-averaged maximum velocity, and velocity-time integral in the two HLHS groups were lower than those in normal controls, and these parameters in the obstructed group were less than those in the unobstructed group. The pulmonary artery pulsatility index in the two HLHS groups was higher than those in normal controls, and it was higher in the obstructed group than in the unobstructed group. There was no statistically significant difference in peak systolic velocity among the three groups (P=0.34).

The antegrade resistance of the pulmonary arteries of HLHS fetuses increase and these pathologcial conditions are more obvious in those with obstructed flow across the atrial septum compared to those with unobstructed flow.