BACKGROUND: Patent ductus arteriosus (PDA) is associated with increased mortality and morbidity in preterm infants. Prophylactic indomethacin results in favorable intermediate outcomes such as reduction of significant PDA, need for surgical ligation, severe intraventricular hemorrhage and serious pulmonary hemorrhage without modifying long-term neurosensory outcomes. Little is known about the effectiveness and safety of prophylactic surgical closure of the PDA in extremely low birth weight (ELBW) infants. OBJECTIVES: To identify and summarize evidence from randomized controlled trials investigating the effectiveness and safety of prophylactic surgical ligation of the PDA on mortality and morbidities of preterm infants less than 1000 g at birth as compared to no prophylaxis or prophylactic cyclooxygenase inhibitors. SEARCH STRATEGY: The standard search strategy for the Cochrane Neonatal Review Group was performed by two review authors. Searches were made of MEDLINE (1966 to December 2006), EMBASE (1980 to December 2006), the Cochrane Central Register of Controlled Trials (The Cochrane Library, Issue 4, 2006), and abstracts of annual meetings of the Society for Pediatric Research (1995 - 2006). Contacts were made with the authors of published articles. SELECTION CRITERIA: Randomized or quazi-randomized controlled trials that enrolled infants less than 28 weeks gestation or less than 1000 g at birth who are on assisted ventilation and/or supplemental oxygen without clinical signs of hemodynamic significance of the ductus arteriosus were considered. Trials addressing prophylactic surgical ligation of the patent ducts arteriosus (i.e. procedure done during the first 72 hours of life) versus no intervention or cyclooxygenase inhibitor prophylaxis were included. The primary outcome was bronchopulmonary dysplasia (BPD). Other important short and long-term neonatal outcomes were also considered. DATA COLLECTION AND ANALYSIS: Standard methods of the Cochrane Collaboration and its Neonatal Review Group were used to assess the methodologic quality of the trials. Retrieved articles were assessed for eligibility and data was abstracted independently by two reviewer authors. Where data were incomplete, the primary investigators were contacted for further information and clarifications. For dichotomous outcomes, relative risk (RR) and its associated confidence interval were calculated. For continuous outcomes, treatment effect was expressed as mean difference and its calculated standard deviation. When appropriate, meta-analysis of pooled data was performed assuming a fixed effect model MAIN RESULTS: Only one eligible study that enrolled 84 ELBW infants was identified. The prophylactic group had ductal ligation performed within 24 hours of life following a pre-specified protocol, while the control group received standard care without indomethacin. Prophylactic surgical ligation of the PDA resulted in a statistically significant reduction of severe stage II or III necrotizing enterocolitis (NEC), [RR 0.25, 95% CI (0.08,0.83), p value 0.02, NNT 5]. The study found no statistically significant difference in mortality, severe grade III and IV intraventricular hemorrhage (IVH), BPD, and retinopathy of prematurity (ROP). Of note, the study was unblinded and underpowered to detect clinically important differences in the above mentioned outcomes. AUTHORS' CONCLUSIONS: Prophylactic surgical ligation of the PDA did not decrease mortality or BPD in ELBW infants. A significant reduction of stage II or III NEC was noted. Based on the current evidence, the high rate of spontaneous closure, availability of effective safe medical therapies, and the potential short and long-term complications of surgical ligation, the use such prophylactic surgical therapy is not indicated in the management of the preterm infants.