Objectives:
The aims of the present study are (1) to determine the erythrocyte CAI and CAll concentrations in SGA and anemic fetuses and to compare them with normal levels, and (2) to examine whether there is any correlation between fetal hypoxia or anemia and isoenzyme concentrations. Methods: Human erythrocyte CAI and CAll concentrations were measured in SGA (n = 25) and anemic (n = 32) fetuses (20-36 weeks' gestation), using enzyme-linked immunosorbent assays (ELISA). The blood gases and pH were measured with an ABL-2c blood gas analyzer. Results and conclusion: In the group of SGA fetuses, there was a tendency for CAI and CAll to be higher than for normal fetuses. The CAI/CAil ratio was also significantly higher than the normal ratio. There were significant correlations between blood A pH and A CAI, A CAll, or A CAt/CAll ratio in this group of fetuses. The levels of CAI, CAll, and CAI/CAII ratio were the same as for normal fetuses in the group of anemic fetuses from red cell isoimmunized pregnancies before their first intrauterine blood transfusion. However, in the group of anemic fetuses after their first blood transfusion, the levels of both isoenzymes were significantly higher than the normal blood levels. Within the latter group there was a significant negative correlation between the A CAI and the percentage of fetal erythrocytes in the circulation.