Exposure to traumatic events during pregnancy may influence pregnancy and birth outcomes. Growing evidence suggests that exposure to traumatic events well before pregnancy, such as childhood maltreatment (CM), also may influence the course of pregnancy and risk of adverse birth outcomes. We aimed to estimate associations between maternal CM exposure and small-for-gestational-age birth (SGA) and preterm birth (PTB) in a diverse US sample, and to examine whether common CM-associated health and behavioral sequelae either moderate or mediate these associations. The Measurement of Maternal Stress (MOMS) Study was a prospective cohort study that enrolled 744 healthy English-speaking participants ≥ 18 years with a singleton pregnancy, who were < 21 weeks at enrollment, between 2013 and 2015. CM was measured via the Childhood Trauma Questionnaire (CTQ) and participants above the moderate/severe cut-off for any of the five childhood abuse and neglect scales were assigned to the CM-exposed group. Common CM-associated health (obesity, depressive symptoms, hypertensive disorders) and behavioral (substance use) sequelae were obtained from standardized questionnaires and medical records. The main outcomes included PTB (gestational age < 37 weeks at birth) and SGA (birthweight < 10%ile for gestational age) abstracted from the medical record. Multivariable logisitic regression was used to test associations between CM, sequeale, and birth outcomes, and both moderation and mediation by CM-related sequelae were tested. Data were available for 657/744 participants. Any CM exposure was reported by 32% of participants. Risk for SGA birth was 61% higher among those in the CM group compared to the non-CM group (14.1% vs. 7.6%), and each subsequent form of CM that an individual was exposed to corresponded with a 27% increased risk for SGA (aOR 1.27, 95% CI 1.05, 1.53). There was no significant association between CM and PTB (9.3% vs. 13.0%, aOR 1.07, 95% CI 0.58, 1.97). Of these sequelae only hypertensive disorders were associated with both CM and SGA and hypertensive disorders of pregnancy did not mediate the association between CM and SGA. Our findings indicate that maternal CM exposure is associated with increased risk for SGA birth and highlight the importance of investigating the mechanisms whereby childhood adversity sets the trajectory for long-term and intergenerational health issues.