[The relationship between flow velocity waveforms of umbilical and fetal middle cerebral arteries and cord blood gas values].

Umbilical artery (UA) and fetal middle cerebral artery (MCA) flow velocity waveforms were obtained from 55 fetuses just prior to elective cesarean section at 36-39 weeks of gestation and the resistance index (RI) was calculated for each waveform. Cord blood samples were obtained from both the umbilical artery and the vein at cesarean section and the blood gas values were measured immediately. The coefficients of correlation between the cord blood gas values and the resistance indices were obtained. 1. UA-RI had a significant negative correlation with pH and Po2, and a positive correlation with Pco2. 2. MCA-RI had a significant positive correlation with pH and Po2, and a negative correlation with Pco2. 3. The UA-RI/MCA-RI ratio had a significant negative correlation with pH and Po2, and a positive correlation with Pco2. 4. The best correlation was found in the UA-RI/MCA-RI ratio, and the UA-RI, MCA-RI and UA-RI/MCA-RI ratios had a closer correlation with umbilical arterial blood gas values than with umbilical venous blood gas values. A Doppler study of fetal blood distribution would be a useful method in the noninvasive assessment of the fetal blood gas state at 36-39 weeks of gestation.