Blood-oxygen transport in first trimester of diabetic pregnancy.

Factors involved in blood-oxygen transport were studied in 46 pregnant women during the first trimester. All had type 1 (insulin-dependent) diabetes and comparisons were made with similar measurements from 19 non-diabetic pregnant women, also in the first trimester. The concentration of hemoglobin A1c (HbA1c) was significantly increased (7.6% versus 4.4%, p less than 0.01) and arterial oxygen saturation was decreased (0.95 versus 0.98 mol/mol, p less than 0.01) in the pregnant diabetics compared with the non-diabetics. The hemoglobin concentration was significantly elevated in the diabetic women (12.9 versus 12.1 g/100 ml, p less than 0.01). Even though the red cell 2,3-diphosphoglycerate content was the same in the two groups, and pH was significantly lower in the diabetic women, hemoglobin-oxygen affinity was slightly increased in the diabetic patients (P50 at actual pH: 26.2 versus 26.7 mmHg, p less than 0.05; P50 at pH 7.40: 27.0 versus 28.0 mmHg, p less than 0.01). The study has demonstrated certain modifications in the blood oxygen transport system in the first trimester of pregnancy of diabetic women that are possibly related to the presence of excess amounts of glycosylated hemoglobin with increased oxygen affinity. This disturbance in maternal oxygen transport, particularly when associated with diabetic vascular disease, may lead to episodes of fetal hypoxia. Such fetal hypoxia may be a pathogenetic factor for the development of congenital malformations in the outcome of diabetic pregnancy.