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RESEARCH PRODUCT

Respiratory Gas Transport in Blood during Pregnancy with Hemoglobin Concentrations Below 12g/100ml

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During pregnancy the conditions for respiratory gas transport in blood and respiratory gas exchange differ from that of non-pregnant healthy women. The hemoglobin concentration and, consequently, the O2 capacity of blood decreases. The arterial CO2 tension falls between the 10th and the 40th week of gestation to values of about 30 mmHg, while the pH of the arterial blood during the same period was found to be nearly constant at an elevated level (7). Investigations of blood O2 affinity during pregnancy led to non-uniform results. Several investigators found no significant change whereas others described a significant decrease of blood O2 affinity in pregnant women and a mean P50 value of about 31 mmHg. Among the factors which are considered to influence the O2 affinity of blood, the intraerythrocytic 2,3-diphospnoglycerate concentration, in particular, increases during pregnancy (11). The aim of this study was to investigate the influence of a reduction of blood hemoglobin concentration below 12g% on the conditions for respiratory gas transport in blood of pregnant women.