OBJECTIVES: To assess clinical characteristics and national charges for maternal hospitalizations and complications associated with cancers during pregnancy in the United States. METHODS: This population-based retrospective study of inpatient preterm complications or delivery and economic burden associated with cancer diagnosed during pregnancy utilized Agency for Healthcare Research and Quality (AHRQ) Healthcare Cost and Utilization Project (H-CUP) Nationwide Inpatient Sample (NIS) data from 2005-2009.  Inclusion criteria included ≥18 years, any maternal diagnoses or procedures on record, and any diagnosis of cancer.  Descriptive analyses were conducted to report the most common forms of cancer, complications of pregnancy, and comorbidities.  Generalized linear models including multivariate logistic and gamma regressions were employed to assess outcomes of preterm births and charges, respectively, based upon patient demographics, primary payer, hospital characteristics, length of stay, Elixhauser comorbidities, preterm labor, abnormalities in fetal heart rate/rhythm, and pre-eclampsia/eclampsia. RESULTS: Overall, 14,190 inpatient cancer discharges in pregnant adults from 2005-2009 were observed.  The mean maternal age was 30.3±6.5 years, with an average length of stay being 5.0±7.8 days.  The national bill summed to $434 million, averaging $31,366 (±71,765) per case.  The most common cancers were Hodgkin’s disease and other lymphomas (27%), breast cancer (15%), leukemias (14%), genitourinary cancers (14%), and thyroid/endocrine cancers (7%).  Some 2,846 full-term births and 2,140 premature births occurred; 321 inpatient fetal deaths/miscarriages were reported.  In cases involving births, regression analyses found that metastatic cancer, solid tumors, and pre-eclampsia/eclampsia were significantly (p≤0.05) associated with preterm delivery.  Increases in total charges were significantly associated with metastatic cancer, chronic blood loss anemia, hypertension, and fluid/electrolyte disorders.  CONCLUSIONS: Some 4986 births were observed among pregnant adults with cancer during 2005-2009, with a large proportion involving premature delivery.  Continued research is warranted concerning the management and long-term implications of cancer and its treatment upon both mothers and their surviving children.