Acute cerebral redistribution in response to invasive procedures in the human fetus

OBJECTIVES: We sought to investigate the fetal hemodynamic response to the acute stress of invasive procedures. STUDY DESIGN: The middle cerebral artery pulsatility index was measured by Doppler ultrasonography before and after 136 invasive procedures (fetal blo od sampling, transfusion, shunt insertion, tissue biopsy, and ovarian cyst aspiration). The response of fetuses submitted to invasive procedures invol ving transgression of the fetal body, such as intrahepatic vein blood sampl ing, was compared with that of control procedures at the placental cord ins ertion. RESULTS: The middle cerebral artery pulsatility index Value fell with fetal blood sampling performed at the intrahepatic Vein (median, -0.26; 95% conf idence interval, -0.35 to -0.15) but not at the placental cord insertion (m edian, 0.05; 95% confidence interval, -0.04 to 0.19). With transfusions, th e middle cerebral artery pulsatility index also fell with procedures at the intrahepatic vein (mean, -0.51; 95% confidence interval, -0.66 to -0.35) b ut not at the placental cord insertion (mean, -0.04; 95% confidence interva l, -0.23 to 0.14). The magnitude of the response was greater with transfusi ons than with blood sampling alone. The middle cerebral artery pulsatility index value also fell with non-fetal blood sampling procedures involving tr ansgression of the fetal body (mean, -0.32, 95% confidence interval. -0.56 to -0.09) but not with control non-fetal blood sampling procedures. The cha nge in the middle cerebral artery pulsatility index was not related to gest ational age, with the youngest fetus showing a fall in the middle cerebral artery pulsatility index value being at 16 weeks' gestation. Although the d egree of response was weakly correlated with the duration of needling (y = -0.21 -0.00014x; R-2 = 0.08; P = .02), multiple logistic regression demonst rated that this was instead a function of the type of the procedure. A resp onse was seen within 70 seconds of fetal puncture. The fetal heart rate did not change significantly with procedures in any of the above-mentioned gro ups. CONCLUSIONS: The human fetus mounts a cerebral hemodynamic response to inva sive procedures involving transgression of the fetal body, which is consist ent with the brain-sparing effect.