RESUMO
OBJECTIVE: To study the effects of maternal smoking on pregnancy outcome and placental histopathology findings. MATERIALS & METHODS: Maternal and labor characteristics and pathological reports were compared between term placentas of complicated and uncomplicated pregnancies of: heavy smokers (>10 cigarettes per day, H-smokers), moderate smokers (<10 cigarettes per day, M-smokers) and non-smokers (controls, N-smokers). RESULTS: Birth-weights were lower in the H-smokers and M-smokers as compared to the N-smokers (p<0.001), with a higher rate of small for gestational age (SGA): 18.2%, 19.2% and 11.4%, respectively (p=0.01). Deliveries among smokers were characterized by higher rates of abnormal fetal heart rate tracings during labor as compared to non-smokers (p=0.01). Rates of placental maternal and fetal stromal-vascular supply lesions was similar between the groups. CONCLUSIONS: Maternal smoking is associated with higher rates of SGA. Tobacco's potential influence is probably through the disruption of normal placental epigenetic patterns, not expressed in placental histopathology lesions.