Improving quality of care is a major healthcare goal; however, the relationship between limited resources and appropriate healthcare distribution has always been problematic. Planning for resource shortages is important for improving healthcare quality. The aim of our study was to evaluate the effects of manpower planning on improvements in quality of care by estimating the effects of medical staffing on readmission within 30 days after discharge.We conducted an observational study using 2011-14 National Health Claim data from 692 hospitals and 633 461 admissions. The database included information on uterine (including adnexa) procedures (195 270 cases) and cesarean deliveries (438 191 cases). The outcome variable was readmission within 30 days after discharge. A generalized estimating equation model was used to evaluate associations between readmission and medical staffing.The number of doctors and the proportion of registered nurses (RNs) were significantly associated with a lower risk of readmission within 30 days (proportion of RNs, Relative Risk (RR): 0.97, P values: 0.0025; number of doctors, RR: 0.96, P values: <0.0001). The number of nurses (RNs + licensed practical nurses) was not associated with readmission within 30 days (RR: 1.01, P values: <0.0001).Our results suggested that higher numbers of doctors and higher proportions of RNs were positively correlated with a lower risk of readmission within 30 days. Human resource planning to solve manpower shortages should carefully consider the qualitative aspects of clinical care and include long-term planning.