Structural changes in placental barrier of smoking mother. A quantitative and ultrastructural study.

Human placental villi from all three trimesters of pregnancy, in 90 non-smoking pregnants and 244 cigarette smoking pregnants, were investigated. In smokers, the numbers of syncytial knots and cytotrophoblastic cells increased, depending on the cigarettes per day, syncytial buds and vasculo-syncytial membranes decreased as the pregnancy proceeded. The mean birth weight and placental weight in smokers were decreased, depending on the cigarettes per day at the third trimester. The ultrastructure of placental villi from smokers were compared with that on non-smokers. The villi from smokers had abnormalities of the microvilli, focal syncytial necrosis, decreased syncytial pinocytotic activity, degenerated cytoplasmic organelles. Using a morphometric method, the basement membranes were measured throughout pregnancy. The mean thickness of the basement membranes of trophoblastic layer and fetal capillary were found to not only increase with the maternal smoking during pregnancy but also attain the maximum in the heavy smokers by the third trimester of pregnancy. There was increased collagen in the villous stroma and shrinkage endothelial changes in fetal capillaries, in smokers the deleterious effect of the cigarette smoking on the placental barrier was heavy damage. As a result of impairment of placental barrier, the transports between mother and fetus were hampered.