Maternal cigarette smoking and fetal oxygen transport: a study of P50, 2,3-diphosphoglycerate, total hemoglobin, hematocrit, and type F hemoglobin in fetal blood.

The current study was undertaken to determine whether the O2 carrying capacity of newborns born to mothers who smoke can accommodate to carbon monoxide poisoning to compensate for the potential tissue hypoxia induced by CO. From a cohort of 1,222 women and newborn infants the total hemogloblin concentration, hematocrit, and carboxyhemoglobin (HbCO) were measured and analyzed with regard to the maternal HbCO level and the number of cigarettes smoked per day. Also, for 100 pairs of mothers, of whom 50 were smokers and 50 nonsmokers, and their newborns, measurements were made of the intraerythrocyte concentration of 2,3-diphosphoglycerate (2,3-DPG), the hemoglobin concentration, and the affinity of hemoglobin for oxygen by determination of O2 tension for 50% of Hb-O2 saturation (P50). The results showed no significant relationship between smoking habits of mothers and their levels of hemoglobin, P50, and 2,3-DPG; only the hematocrit was slightly increased in smoking mothers. However, in fetal blood a significant correlation was found between the number of cigarettes smoked per day and levels of hemoglobin, hematocrit, and P50. The P50 decreased in relationship to the increase in maternal HbCO. The P50 change was brought about by an increase in hemoglobin F found in the fetuses of mothers who smoked. Although all these changes were statistically significant, these mechanisms of acclimatization to CO poisoning appeared trivial in magnitude. It is concluded that the human fetus does not have a biologic capacity to accommodate to maternal cigarette smoking, and therefore the fetus is particularly susceptible to the adverse effects of cigarette smoking.