Mental illness (MI), substance abuse (SA), and intentional injury (II) are known individual risk factors for adverse pregnancy outcomes. Their combined association with preterm birth (PTB) and low birth weight (LBW) remains relatively unexplored. We examined hospital utilization for the co-occurrence of II and MI or SA in pregnant women in Massachusetts and assessed their interactive association with PTB and LBW. This retrospective cohort study used ICD-9 and E-codes reported on linked birth and hospital utilization data to identify MI, SA, and II diagnoses during pregnancy for 176,845 Massachusetts resident women who delivered during 2002-2004. Adjusted odds ratios (OR) for the independent and joint associations of MI, SA, and II on PTB and LBW were calculated. Two thousand two hundred and eight women (1.6%) had a prenatal MI visit, 834 (0.5%) a prenatal SA visit, and 847 (0.5%) a prenatal II visit. Among them 163 women had MI and II visits and 69 had SA and II visits. SA, MI, and II were all significant predictors of LBW and PTB. Women with both SA and II had higher odds of PTB (OR 2.7 95% CI 1.3-5.7) and LBW (OR 5.3 95% CI 3.9-7.3) than women with neither diagnosis. Prenatal MI, SA, and II are risk factors for LBW and PTB. Women with SA and II co-diagnoses have greater risk of LBW and PTB than women with neither diagnosis. Screening, timely diagnosis, and treatment of women with co-occurring morbidities, particularly II and SA, should be incorporated into reproductive and perinatal health programs.