Glycosylated hemoglobin in diabetic and nondiabetic pregnancies

Fasting serum glucose and hemoglobin A1 (HbA1) levels were lower in diabetic and nondiabetic patients during the third trimester of pregnancy than in similar groups of nonpregnant subjects. HbA1 levels decreased in nine of 15 nondiabetic subjects and in nine of ten diabetic patients as pregnancy advanced. The change in HbA1 observed during pregnancy may be due to lower fasting glucose concentrations, but other physiologic changes of pregnancy such as expansion of the red cell mass and variations in fetal hemoglobin levels also may contribute to the decrease in HbA1 in the third trimester of pregnancy.