Objective To assess whether the implementation of an intrapartum training package (PROMPT (PRacticalObstetric Multi-Professional Training)) across a health service reduced the proportion of term babies born with Apgar score <7 at 5 min (<75mins). Design Stepped-wedge cluster randomised controlled trial.Setting Twelve randomised maternity units with ≥900 births/year in Scotland. Three additional units wereincluded in a supplementary analysis to assess the effect across Scotland. The intervention commenced in March 2014 with follow-up until September 2016.Intervention The PROMPT training package (Second edition), with subsequent unit-level implementation ofPROMPT courses for all maternity staff.Main outcome measures The primary outcome was the proportion of term babies with Apgar<75mins.Results 87 204 eligible births (99.2% with an Apgar score), of which 1291 infants had an Apgar<75mins were delivered in the 12 randomised maternity units. Two units did not implement the intervention. The overall Apgar<75mins rate observed in the 12 randomised units was 1.49%, increasing from 1.32% preintervention to 1.59% postintervention. Once adjusted for a seculartime trend, the ’intention-to-treat’ analysis indicated a moderate but non-significant reduction in the rate of term babies with an Apgar scores <75mins following PROMPT training (OR=0.79 95%CI(0.63 to 1.01)). However, some units implemented the intervention earlier than their allocated step, whereas others delayed the intervention. The content and authenticityof the implemented intervention varied widely at unit level. When the actual date of implementation of the intervention in each unit was considered in the analysis,there was no evidence of improvement (OR=1.01 (0.84 to 1.22)). No intervention effect was detected by broadening the analysis to include all 15 large Scottish maternity units. Units with a history of higher rates of Apgar<75mins maintained higher Apgar rates during the study (OR=2.09 (1.28 to 3.41)) compared with units with pre-study rates aligned to the national rate.Conclusions PROMPT training, as implemented, had no effect on the rate of Apgar <75mins in Scotland during the study period. Local implementation at scale was found to be more difficult than anticipated. Further research is required to understand why the positive effects observed in other single-unit studies have not been replicated in Scottish maternity units, and how units canbe best supported to locally implement the intervention authentically and effectively.Trial registration number ISRCTN11640515.