CHANGES IN BLOOD-FLOW VELOCITY WAVE-FORMS FOLLOWING FETAL BLOOD-SAMPLING

The umbilical artery, aorta, and middle cerebral artery pulsatility in dices were investigated by pulsed Doppler ultrasound in 73 fetuses at 18-37 weeks of gestation, before and after fetal blood sampling perfor med either at the placental cord insertion (n = 46) or at the intrahep atic vein (n = 27). At the end of the procedure, after randomization, 35 fetuses were infused amounts of normal saline equal to the blood vo lume withdrawn, and 38 fetuses served as controls. Following blood sam pling, the umbilical artery pulsatility indices decreased both in cont rols (p = 0.004) and in the saline group (p = 0.006). The middle cereb ral artery velocity waveforms exhibited similar changes only in contro ls (p = 0.01), and no changes in fetal heart rate and aortic pulsatili ty indices were recorded in either group. The changes in blood flow ve locity waveforms did not correlate with gestational age and the blood volume sampled, and were similar whether the site of sampling was the placental cord insertion or the intrahepatic vein. In 10 acidemic and/ or hypoxemic fetuses, pulsatility indices in the umbilical and middle cerebral arteries were not modified by the blood sampling procedure. T he release of vasoactive substances is most likely the cause of dimini shed vascular resistances following fetal blood sampling. Hypoxemic/ac idemic fetuses may fail to mount a normal vasodilative response to nee dle puncture.