Objective: To undertake a cost minimisation study of ST analysis (STan) plus cardiotocograpy (CTG) compared to CTG alone. Design: Cost-minimisation analysis alongside a randomised controlled trial [(1)](#ref-0001). Setting: A tertiary level maternity centre in Adelaide, South Australia. Population: Women in labour ≥36 weeks gestation, with a clinical indication for continuous electronic fetal monitoring. Methods: We utlilised a health service perspective covering randomisation to final maternal and neonatal discharge, including readmissions. Primary analysis was intention to treat, with secondary per protocol analysis. Post hoc analyses were conducted by sub-groups and after exclusion of outliers. Main outcome measure: Average cost per mother/baby dyad. Results: Costs were calculated for 957/968 patients (98.9%) using hospital financial data. There was no statistically significant evidence of difference between the two study arms but lower costs observed in the STan arm. Average cost per mother/baby dyad was AUD12,768 for Stan+CTG, compared with AUD15,027 for CTG alone. Lower costs were mainly due to lower neonatal costs, particularly for critical care. Maternal labour cost was nearly identical in the two arms. The difference was still shown, although with reduced magnitude, when outliers were removed and increased with a per protocol analysis. Conclusion: While not statistically significant, reduced costs were observed in the CTG+STan arm (average reduction per mother / baby dyad = AUD2,259).