Pregnant women with high levels of nicotine dependence are the least likely to quit smoking spontaneously during pregnancy or to benefit from smoking cessation interventions. In the general population, there is increasing evidence of a relationship between smoking, nicotine dependence, and exposure to childhood trauma. We examined the relationship of childhood trauma to several measures of nicotine dependence and evaluated whether this relationship was mediated by major depressive disorder or depressive symptom severity in pregnant smokers. Moderate to extreme levels of childhood trauma were significantly related to smoking within 5 minutes or less of waking, and to the Behavioral Choice-Melioration, Negative Reinforcement, and Tolerance subscales of the Wisconsin Inventory of Smoking Dependence Motives (WISDM-68) scale. The relationships between childhood emotional abuse and the WISDM-68 Total and Negative Reinforcement subscale were partially mediated by depressive symptoms. Results suggest that childhood trauma may be a risk factor underlying nicotine dependence in pregnant smokers. Increased understanding of the relationship of affect regulation to smoking in individuals with childhood trauma histories may aid in the development of more effective treatments of nicotine dependence for this population of smokers.