The influence of anemia on respiratory gases and acid base parameters of the fetus.

Fetal blood samples were collected by cordocentesis from 82 pregnant women; 12 of whom had severe forms of Rh isoimmunization, while 70 comprised the control group. The mean hematocrit value in the group under investigation was 15.72 +/- 3.62% and indication of severe anemia. The pH value in this group was 7.31 +/- 0.06; pCO2 partial pressure 6.36 +/- 0.64; O2-2.65 +/- 0.89 kPa; bicarbonate 23.84 +/- 3.02 mMol/l: base excess was -2.72 +/- 2.66 mMol/l and saturation 28.66 +/- 15.56%. In the control group the following values were established: pH -7.386 +/- 0.05; partial pressure pCO2-4.980 +/- 0.31 kPa; O2--4.960 +/- 0.90 kPa; bicarbonate 21.560 +/- 0.27 mMol/l; base excess -2.30 +/- 0.90 mMol/l and saturation 67.23 +/- 11.60%. The pH, partial pressure O2 and saturation values were significantly lower, while partial pressure CO2 was significantly higher in the investigated group than in the control group. Bicarbonates and base excess do not change significantly in the presence of anemia. Fetal blood sampling carried out by means of cordocentesis is the most reliable method for assessment of the degree of fetal anemia. The values of acid base parameters and of blood gases are an indication of either respiratory, respiratory-metabolic or metabolic acidosis. The possibilities of prenatal diagnostics, undoubtedly, contribute to a significant reduction of perinatal mortality.