Ultrastructure of human umbilical veins: observations on veins from newborn children of smoking and nonsmoking mothers

. The umbilical vein was chosen as a possible model for evaluating the vascular injury provoked by tobacco‐smoking in humans. Umbilical veins from newborn children of 4 nonsmoking and 4 heavy‐smoking mothers were examined in the transmission electron microscope. Severe changes were present in the intima and media of veins in the heavy‐smoker group. Pronounced edema was found in the subintimal space, combined with destruction of intimal elastic membranes, a marked decrease in collagen content and a proliferative reaction of the myocytes. Similar changes have been observed in animal studies involving exposure to carbon monoxide, hypoxia or nicotine. The present study supports the concept that tobacco‐smoking is harmful to the human vascular system and illustrates the mechanism through which the vascular injury is provoked in heavy smokers. The study also indicates that tobacco‐smoking causes severe damage during pregnancy to the cord. Similar pronounced changes might be expected in the newborn children of smoking mothers. Tobacco‐smoking should therefore be abandoned during pregnancy. Smoking during pregnancy carries a high risk for the fetus, including an increased risk of abortion and stillbirth, as well as death soon after delivery. It is also well established that the average weight of newborn children of smoking mothers is 150–300 g less than that of those born to nonsmoking mothers (1, 5, 11, 12, 17). The present study evaluates the ultrastructural changes found in the umbilical veins of newborn children of heavy‐smoking mothers compared with a control group.