Correlation between 2,3-diphosphoglycerate and red cell mass in the third trimester of pregnancy.

In 30 non-anemic, and in 7 non-thalassemic, anemic pregnant women the red cell mass (RCM) was determined at 32-36 weeks of pregnancy, using isotopes, and was correlated with red cell 2,3-DPG, using the method of Keitt. The increase in 2,3-DPG in pregnant women with low RCM was in the same range as in those with increased RCM. Thus, 2,3-DPG can not be used to diagnose a RCM deficit in pregnancy. The relationship between 2,3-DPG and RCM in the third trimester was complex: in the 7 anemic women there was an inverse relationship, which failed to reach statistical significance, probably because of the small number of cases; in the 30 non-anemic women there was a significant, positive correlation between 2,3-DPG and RCM. The cause of this positive relationship needs further investigation.