Background: To evaluate the relationship between periconceptional (period before and/or after conception) substance use and unfavorable pregnancy contexts, including unintended pregnancy. Materials and Methods: This is a cross-sectional analysis of English-or Spanish-speaking women aged 16-44 years with pregnancies <24 weeks' gestation presenting to pregnancy testing clinics and enrolled between June 2014 and June 2015. Participants self-reported periconceptional substance use (tobacco, alcohol, marijuana, and other illicit substances during the 3 months before enrollment), and pregnancy ''contexts,'' including pregnancy intention, wantedness, planning, timing, desirability, and happiness. Multivariable logistic regression was performed adjusting for potential confounding variables. Results: We enrolled 123 women, averaging 27 -6 years, and mean gestational age 7.5 -3.0 weeks. Most participants were black, non-Hispanic (37%), or Hispanic (46%), and chose to complete the study in English (69%). Sixty-five percent participants reported use of one or more substances during prior 3 months: alcohol (54%), tobacco (31%), and marijuana (21%). In multivariate analysis, periconceptional alcohol use was associated with increased odds of unintended or ambivalent pregnancy and unwanted or mixed feelings regarding pregnancy (odds ratios [OR] = 3.29, 95% confidence interval [CI] 1.08-10.08 and OR = 2.81, 95% CI 1.07-7.36, respectively). Weekly or daily tobacco use was associated with unhappiness about pregnancy (OR = 7.56, 95% CI 1.65-34.51) and undesired or unsure pregnancy (OR = 4.00, 95% CI 1.14-14.06). Conclusions: Periconceptional alcohol or tobacco use demonstrates increased odds of specific unfavorable pregnancy contexts, including pregnancy described as undesired, unintended, unwanted, and unhappiness with pregnancy. Primary prevention of periconceptional substance use and the negative effects of alcohol and tobacco may be improved by increasing contraception access for women at risk for unfavorable pregnancy contexts.Keywords: alcohol; pregnancy; tobacco; unintended pregnancy; unplanned pregnancy However, focusing on preconception care in this way may be insufficient as it assumes that women have control over their reproductive lives, that contraception never fails, that all pregnancies are planned, and that such assumptions are inherently flawed. 5,6 For example, purposeful abstinence regarding tobacco, alcohol,