Smoking during pregnancy is the single most modifiable risk factor for poor birth outcomes, yet it remains prevalent among low-income women. This study examined factors associated with continued smoking and quitting among pregnant women. A total of 2,203 Medicaid-eligible pregnant women were screened at their first enhanced prenatal services visit for risk factors including demographics, health behaviors (smoking, alcohol and drug use), mental health (history of mental health disorders, current depressive symptoms), and stress. Smoking status was divided into non-smokers, quitters (quit smoking since learning of pregnancy), and continuing smokers. Descriptive statistics and logistic regression models were used to describe the sample and analyze relationships between smoking status and other characteristics. Overall, 57% were non-smokers, 17% quitters, and 26% continuing smokers. Approximately 18% had severe depressive symptoms, 53% had a high stress score, and 33% had a history of mental health problems. Younger women had lower odds of continued smoking as compared to both non-smokers (OR = 0.48, p < 0.01) and quitters (OR = 0.56, p < 0.05). Older women with less than a 12th grade education had higher odds of continued smoking (OR = 2.17, p < 0.01) and quitting (OR = 1.62, p < 0.05) as compared to non-smokers. Alcohol use (OR = 2.81, p < 0.05) and drug use before pregnancy (OR = 5.32, p < 0.01) predicted continued smoking compared to non-smoking. Women with a mental health history (OR = 1.81, p < 0.01) and high stress scores (OR = 1.39, p < 0.05) had higher odds of continued smoking compared to non-smokers. Mental health history, stress, demographics, current alcohol and past drug use are strongly related to continued smoking in this population.