Maximal velocity of fetal pulmonary venous blood flow

Introduction
Doppler imaging of foetal pulmonary veins plays a crucial role in prenatal cardiology centres. Therefore, we established reference ranges for maximal fetal pulmonary venous blood flow velocity for our unit.

Material and methods
A database of fetal ultrasound and echocardiographic examinations was analysed retrospectively. Healthy fetuses with no evidence of heart defect or any abnormality at the time of examination were selected as a study group. Fetuses with functional or morphological anomalies were excluded. The obtained data included: gestational age of pregnancy according to last menstrual period, maximal velocity of blood flow through pulmonary veins (Vmax for PVs), prenatal cardiological diagnosis, extracardiac anomalies, and extracardiac abnormalities.

Results
Ultrasound data were collected at 18–39 weeks of gestation in singleton pregnancies. The study group contained 184 healthy fetuses. Scatter graph and reference ranges for their Vmax for PVs during pregnancy were prepared. The regression equation for Vmax for PVs as a function of gestational age (GA) in days was: Vmax for PVs (cm/sec) = 0.1 x GA (in days) + 5.5 (r = 0.45, CI 0.95).

Conclusions
We presented normal ranges for pulmonary vein Doppler flow for the 18th–38th week of gestation in fetuses with normal heart anatomy, showing a steady increase towards the term in statistical analysis. However, each case should be approached individually because interpretation of the calculated values might not be very easy or straightforward.