Effect of smoking on red cell oxygen transport and release in diabetic pregnancy.

In order to investigate the effect of smoking on the red cell oxygen transport and release in pregnant diabetic women, 23 smokers and 23 non-smokers were studied in the third trimester. The two groups were comparable with regard to blood glucose regulation, as the median concentration of blood glucose and glycosylated hemoglobin (Hb A1c) did not differ. Red cell 2, 3-diphosphoglycerate (2, 3-DPG) levels were significantly lower in the smokers than in the non-smokers (16.5 vs 17.8 mumol/gHb, p less than 0.01). P50 of the oxyhemoglobin dissociation curve at actual pH and at pH 7.40 was also significantly lower in the smokers (25.9 vs 26.9 mmHg, p less than 0.01, and 26.5 vs 27.8 mmHg, p less than 0.01 respectively). Red cell 2, 3-DPG was significantly correlated with P50 at pH 7.40 (r = 0.73, p less than 0.001). Arterial oxygen saturation was reduced to the same degree in smokers and in non-smokers, as compared with healthy non-smoking pregnant women and no adaptive increase in the hemoglobin concentration occurred in the pregnant diabetic smokers. The study suggests that smoking in pregnant diabetic women impairs the adaptive increase in 2, 3-DPG associated with diabetes-induced hypoxia.