Blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus: reference ranges from 13 weeks to term.

To establish reference ranges for blood flow velocity waveforms of the fetal main pulmonary artery and the ductus arteriosus during the second and third trimesters of pregnancy. A prospective cross-sectional echocardiographic study was performed in 222 normal fetuses from 13 to 41 weeks of gestation using high resolution/color Doppler ultrasound equipment. Gestational age-specific reference ranges are given for peak velocity across the pulmonary valve, velocities in the ductus arteriosus, peak systolic velocity in the ductus arteriosus-to-peak velocity across the pulmonary valve ratio, ductal systolic velocity-to-diastolic velocity ratio, ductal resistance index and ductal pulsatility index. In the ductus arteriosus, increasing fetal heart rate was significantly associated with increasing end-diastolic velocity and decreasing systolic-to-diastolic ratio, decreasing resistance index, and decreasing pulsatility index. Based on a prospective study in more than 200 normal fetuses, the data provide gestational age specific reference ranges for blood flow velocity waveforms of the fetal pulmonary artery and the ductus arteriosus. The reference ranges may be helpful in prenatal diagnosis of cardiac malformations and ductal obstruction from 13 to 41 weeks of gestation.