The effect of cordocentesis on umbilical and middle cerebral artery blood flow velocity waveforms

Objective To investigate the effect of cordocentesis on the umbilical and fetal cerebral circulation. Design Cross sectional study. Setting Department of Obstetrics and Gynaecology, Regional Referral Centre for Fetal Medicine, Klagenfurt Hospital, Austria. Subjects Thirty pregnant women undergoing diagnostic cordocentesis at 18 to 38 weeks' gestation. Interventions The pulsatility index (PI) in the umbilical artery and fetal middle cerebral artery was measured by pulsed Doppler ultrasound before and immediately after cordocentesis. Main outcome measures Change in umbilical artery PI and middle cerebral artery PI. Results Cordocentesis was associated with a significant decrease in both umbilical artery PI (median −0.18, range −2.21 to 1.5, P<0.004) and middle cerebral artery PI (mean -0.15, SD 0.32, P<0.03) and the decrease in umbilical artery PI was most marked when cordocentesis was performed transplacentally. In four cases, there were absent or reversed frequencies at the end of diastole (EDF) in the umbilical artery before cordocentesis, and in all cases there were positive EDF after the procedure. In contrast, one of the 26 cases with positive EDF developed reversed EDF following the procedure. Conclusions Acute alterations in the waveforms from both the umbilical and fetal cerebral circulation can be induced by cordocentesis. The decrease in resistance in the fetoplacental circulation could be attributed to the release of vasodilators, and the increase in resistance observed in some cases could be secondary to arterial vasospasm. Better understanding of the underlying mechanisms might help in making cordocentesis a safer procedure.