Maternal cigarette smoking and placental function : morphology, oxygen diffusive capacity, amino acid and zinc transport, and trace element content
Maternal smoking during pregnancy is known to result in an increased incidence of intra-uterine growth retardation. This in part may be due to deleterious effects on the placenta, which is the conduit between the mother and fetus. This study was designed to investigate the effect of maternal smoking on placental function: morphometry, oxygen diffusive capacity, trace element content (zinc and cadmium), microvillous border membrane (MVBM) vesicle zinc and alanine uptake, and placental enzyme activity. The magnitude of maternal smoking and confounding factors were determined twice by questionnaire during pregnancy and confirmed by plasma cotinine; a total of 105 placentae were collected. Morphological changes in membrane thickness, and chrionic villi composition were observed with maternal smoking, however these changes were not great enough to affect the placental oxygen diffusive conductance. Placental cadmium content increased with maternal smoking and also correlated with placental zinc content. There was no correlation for cadmium or zinc with placental metallothionein. MVBM vesicle uptake of zinc exhibited no differences between smoking and non-smoking groups. Similarly, MVBM vesicle sodium-independent alanine uptake exhibited no difference, however sodium-dependent alanine uptake was greater in the smoking group. Placental cytochrome P450 ethoxyresorufin-O-deethylase activity was greater in the smoking group placentae compared to the non-smoking group, however quinone reductase activity was unaffected by maternal smoking. The overall findings of this study extend knowledge regarding the impact of maternal smoking on placental function and support current clinical advice for pregnant mothers to stop smoking during pregnancy.