Background Obstetric brachial plexus palsy, a complication of childbirth, occurs in 1-3 per 1000 live births internationally. Traction and/or compression of the brachial plexus is thought to be the primary mechanism of injury and this may occur in utero, during the descent through the birth canal or during delivery. This results in a spectrum of injuries that vary in severity, extent of damage and functional use of the affected upper limb. Most infants receive treatment, such as conservative management (physiotherapy, occupational therapy) or surgery; however, there is controversy regarding the most appropriate form of management. To date, no synthesised evidence is available regarding the effectiveness of primary conservative management for obstetric brachial plexus palsy. Objectives The objective of this review was to systematically assess the literature and present the best available evidence that investigated the effectiveness of primary conservative management for infants with obstetric brachial plexus palsy. Search strategy A systematic literature search was performed using 14 databases: TRIP, MEDLINE, CINAHL, AMED, Web of Science, Proquest 5000, Evidence Based Medicine Reviews, Expanded Academic ASAP, Meditext, Science Direct, Physiotherapy Evidence Database, Proquest Digital Dissertations, Open Archives Initiative Search Engine, Australian Digital Thesis Program. Those studies that were reported in English and published over the last decade (July 1992 to June 2003) were included in this review. Selection criteria Quantitative studies that investigated the effectiveness of primary conservative management for infants with obstetric brachial plexus palsy were eligible for inclusion in this review. This excluded studies that solely investigated the effect of primary surgery for these infants, management of secondary deformities and the investigation of the effects of pharmacological agents, such as botulinum toxin. Data collection and analysis Two independent reviewers assessed the eligibility of each study for inclusion into the review, the study design used and its methodological quality. Where any disagreement occurred, consensus was reached by discussion. Studies were assessed for clinical homogeneity by considering populations, interventions and outcomes. Where heterogeneity was present, synthesis was undertaken in a narrative format. Results Eight studies were included in the review. Most were ranked low on the Hierarchy of Evidence (no randomised controlled trials were found), and had only fair methodological quality. Conservative management was variable and could consist of active or passive exercise, splints or traction. All studies lacked a clear description of what constituted conservative management, which would not allow the treatment to be replicated in the clinical setting. A variety of outcome instruments were used, none of which had evidence of validity, reliability or sensitivity to detect change. Furthermore, less severely affected infants were selected to receive conservative management. Therefore, it is difficult to draw conclusions regarding the effectiveness of conservative management for infants with obstetric brachial plexus palsy. Conclusions There is scant, inconclusive evidence regarding the effectiveness of primary conservative intervention for infants with obstetric brachial plexus palsy. Further research should be directed to develop outcome instruments with sound psychometric properties for infants with obstetric brachial plexus palsy and their families. These outcome instruments should then be used in well-designed comparative studies.