Over the past 30 years, maternal-fetal surgical approaches have evolved for repair of certain cases of congenital abnormalities. Most such anomalies have a high risk of rapid fetal deterioration or impaired organ development. Open fetal surgery was first performed in 1981; minimally invasive endoscopic approaches have emerged as an option for some cases. This report was commissioned by the United States Agency for Healthcare Research and Quality. The aim of this review was to assess current evidence on maternal-fetal surgery for surgical repair of fetal abnormalities. Data were obtained from a MEDLINE search of articles published from 1980 to 2010. Seven types of congenital abnormalities treated in utero were included in the search: twin-twin transfusion syndrome, obstructive uropathy, congenital diaphragmatic hernia, myelomeningocele, thoracic lesions, cardiac malformations, and sacrococcygeal teratoma. Using pilot-tested standardized data collection forms, data from 1341 articles were extracted independently by 2 reviewers, with discordance resolved by a third party. The following information was extracted and analyzed: criteria for inclusion, fetal diagnostic procedures, study design, country and setting, type of surgery, comparators used, length of follow-up, fetal and maternal outcomes, and adverse events. Among the 1341 articles, data from 3 randomized controlled trials and studies of 166 unique study populations were obtained. The bulk of the evidence was observational (70% were case series [n = 116], 36% were retrospective [n = 22], and 7% were prospective cohorts [n = 11]). The most studied condition, twin-twin transfusion syndrome, provided data from 84 studies including 2532 pregnancies treated with laser ablation. Congenital diaphragmatic hernia accounted for 503 pregnancies; each of the remaining 5 conditions involved less than 500 pregnancies. Criteria for inclusion were poorly defined. Typical outcomes measured were survival to birth, preterm birth, and neonatal death. Data on longer-term outcomes were sparse but included pulmonary, renal, and neurologic status and developmental milestones. Very few studies provided information on maternal outcomes. These findings show that the quality of current studies on maternal-fetal surgery and the strength of the available evidence are inadequate to draw conclusions and optimally inform care.