The acute effect of smoking on uteroplacental blood flow in normotensive and hypertensive pregnancy.

The acute effect of smoking on uteroplacental blood flow was studied by the 133Xe method in 12 normotensive and 11 hypertensive pregnant women at term. A standard cigarette caused an acute decrease in intervillous blood flow in the normotensives but normalized within 15 minutes. In the other group, smoking produced a progressive increase in this flow, whose basal presmoking value lower in the hypertensive women. The myometrial blood flow was equal in both groups before smoking but significantly higher in the hypertensive group immediately afterwards. Smoking produced a constant increase in systolic, diastolic and mean arterial blood pressure in the normotensive women. In the other, diastolic and mean arterial blood pressure increased only temporarily, while systolic blood pressure remained unchanged. Heart rate increased in both groups. Repeated decreases in the intervillous blood flow could explain growth retardation of the fetus and some other complications of pregnancy in normotensive smokers. The authors assume that postischemic reactive hyperemia in the uterine vessels caused the increased flow in hypertensive pregnant women after smoking but cannot recommend it as beneficial because of the increased placental transfer of the harmful elements found in tobacco smoke.