Hospital service area (HSA) and Hospital referral region (HRR) are significant in organizing maternal care resources in hierarchical medical systems. This quantitative study aims to delineate HAS and HRR by using obstetrics medical record data reflecting patients' medical behavior to improve the efficiency of the utilization of medical resources. The Dartmouth method and an improved version that considers the administrative division was applied to delineate HSA and HRR by using the obstetrics medical records in Hubei Province of China in 2016. The result shows that 117 Dartmouth HSAs have a strong correlation with the county boundaries and 22 Dartmouth HRRs are highly coincident with the prefecture boundaries in Hubei. In addition, 25 improved Dartmouth HRRs within prefecture boundaries and core areas serving patients across prefecture boundaries have been identified. Based on the above results, two sets of hierarchical healthcare systems were constructed, respectively, which can provide methods and references for delineating HAS and HRR in the hierarchical medical systems in other regions of China and developing countries. The findings of this study shed light on future research and policymaking in the spatial organization of medical resources for improving the efficiency and equity in maternal care delivery.