Relationship between birth weight and umbilical Doppler blood flow velocity waveforms during the third trimester of pregnancy.

OBJECTIVES: The Doppler ultrasound method for recording blood flow velocity waveforms in the fetal umbilical arteries is now widely used as an indicator of fetal well-being. This study was conducted to investigate the impact of umbilical placental resistance level on fetal growth development. METHODS: Maximal flow velocity waveforms were recorded from the umbilical artery in 108 pregnant women including 50 with normal pregnancies, 3 with previous death in utero, and 55 with moderate arterial hypertension corrected by resting only. All the newborn infants had a normal birth weight (BW between the 10th and the 90th percentile for the gestational age at birth). Doppler measurements were performed between 25 to 38 weeks of gestation. The placental resistance index (PRI) derived from blood flow velocity measurements was determined. RESULTS: Data were grouped in two-week intervals according to the age of gestation at Doppler examination. We found an inverse close relationship between BW and PRI which can be described by a linear function of PRI in each interval. BW increased with the decrease in PRI. CONCLUSIONS: Our findings suggest that umbilical placental resistance level determines fetal growth development and birth weight during pregnancies without placental insufficiency.