Effects of Maternal Smoking on Placental Structure and Function

The adverse effect of maternal smoking on fetal birth weight is a well-established fact, but the role of the placenta in this phenomenon is not fully understood. During the last 4 years, we have determined the effects of smoking on placental structure and function in Aberdeen women. Mothers were interviewed and completed a questionnaire at their first antenatal clinic and again at their clinic at the 34th week of gestation. The questionnaires established smoking habit (including brand of cigarette smoked) and also determining factors that might confound the study, such as intake of alcohol and caffeine and exposure to environmental tobacco smoke. Medical records were kept, and only healthy subjects with normal uncomplicated pregnancies were included. Plasma cotinine was estimated from a blood sample taken at the 34th-week clinic (all procedures on this project had prior approval of the local ethics committee), and this was used as an objective measure of smoking habit. At delivery, maternal and fetal blood samples were taken and randomized samples of placental tissue were obtained for morphometry, enzyme and heavy metal analysis, and transport studies. Data are presented as the mean ± standard error of the mean. Birth weights of the children born to smokers were 3421 ± 59 g (n = 56), and to nonsmokers they were 3534 ± 75 g (n = 37).