BACKGROUND: The Australasian Maternity Outcomes Surveillance System (AMOSS) conducts surveillance and research of rare and serious conditions in pregnancy. This multi-centre population health study is considered low risk with minimal ethical impact. OBJECTIVE: To describe the ethics/governance review pathway undertaken by AMOSS. METHOD: Prospective, descriptive study during 2009-2011 of the governance/ethical review processes required to gain approval for Australian and New Zealand (ANZ) maternity units with more than 50 births per year (n = 303) to participate in AMOSS. RESULTS: Review processes ranged from a single application for 24 NZ sites, a single application for eligible hospitals in two Australian states, full Health Research Ethics Committee (HREC) applications for individual hospitals, through simple letters of support. As of September 2011, 46 full/expedited ethics applications, 131 site governance applications and 136 letters of support requests were made over 33 months, involving an estimated 3261 hours by AMOSS staff/investigators, and an associated resource burden by participating sites, to obtain approval to receive nonidentifiable data from 291 hospitals. CONCLUSION: The AMOSS research system provides an important resource to enhance knowledge of conditions that cause rare and serious maternal morbidity. Yet the highly variable ethical approval processes required to implement this study have been excessively repetitive and burdensome. This process jeopardises timely, efficient research project implementation, without corresponding benefits to research participants. The resource burden to establish research governance for AMOSS confirms the urgent need for the Harmonisation of Multi-centre Ethical Review (HoMER) to further streamline ethics/governance review processes for multi-centre research.