The global burden of complications from unsafe abortion is thought to be high, but difficult to measure. A systematic review was conducted to describe the prevalence and type of complications of abortion among women hospitalized for treatment of abortion complications in settings where abortion is generally considered unsafe. There were 43 hospital-based studies reporting on severity and type of complications of abortions, but definitions varied substantially. The proportion of women treated in facilities for severe complications ranged from a median of 1.6% (range, 0.1%-10.8%) for renal failure to 7.2% (range, 0.1%-43.9%) for severe trauma. Heterogeneity of study designs and definitions makes comparisons difficult. Therefore, it is recommended that standardized designs and definitions are used in future studies of abortion complications. © 2012 Published by Elsevier Ireland Ltd. on behalf of International Federation of Gynecology and Obstetrics.