Umbilical and middle cerebral artery blood velocimetry: relationship with placental volume

To investigate the relationship between placental volume and the resistance of fetal arteries: umbilical and middle cerebral.

In 82 pregnant women with unaffected pregnancy between 14 and 40 weeks of gestation measurements of placental volume were made according to the parallel planimetric technique. Doppler examinations of umbilical and middle cerebral arteries were performed by means of a duplex system.

PI in the umbilical artery (PIUA) correlated significantly negatively with placental volume, whereas no significant correlation was found for the PI in the middle cerebral artery (PIMCA) and placental volume. Middle cerebral artery to umbilical artery PI ratio (PIMCA/PIUA ratio) showed significant positive correlation with placental volume. PIUA showed significant negative correlation with the relative volume of placenta (expressed as multiple of median for the actual gestational age) before 25 weeks of gestation and weak positive correlation with the relative volume of placenta after 25 weeks of gestation. PIMCA showed weak negative correlation with the relative volume of the placenta after 25 weeks of gestation and no correlation before 25 weeks. PIMCA/PIUA ratio showed significant positive correlation with relative placental volume before 25 weeks and significant negative correlation with relative placental volume after 25 weeks.