Cigarette smoking in pregnancy: differences in peripheral circulation between smokers and non-smokers

Ten smokers and ten non-smokers were followed serially from 12 to 16 weeks of pregnancy to six weeks postnatally. Measurements of calf and foot blood flow and toe and finger skin temperature were made at 4 to 6 week intervals in both groups, and the acute effects on the peripheral circulation of smoking one standard cigarette were also measured in the smokers at each stage of pregnancy. Comparison between the smokers and non-smokers showed that in the last trimester of pregnancy smokers had significantly higher foot blood flow and toe and finger temperature than non-smokers. These circulatory variables rose during the period of pregnancy studied in smokers but altered little in non-smokers. There was no significant difference in calf blood flow between the groups. Smoking a cigarette during pregnancy caused a fall in foot blood flow and in finger and toe skin temperature. Smoking increased calf blood flow between 12 and 25 weeks of pregnancy but decreased it in late pregnancy. Previous investigations of blood flow in pregnancy have not differentiated between smokers and non-smokers. It is suggested that the rise in foot blood flow and skin temperature believed to occur generally during pregnancy applies mainly to smokers. Some possible reason for differences in skin blood flow between smokers and non-smokers in pregnancy are discussed.