Objective: To evaluate the effectiveness of an innovative strategy to improve implementation of evidence-based guidelines on the management of hypertension in pregnancy compared to a common strategy of professional audit and feedback. Design: Cluster randomized controlled trial (c-RCT). Setting: Sixteen Dutch hospitals. Population: All patients with a hypertensive disorder during pregnancy who were admitted to one of the participating hospitals between April 1st 2010 and May 1st 2011, were suitable for inclusion; the only exclusion criterion was the presence of lethal fetal abnormalities. Methods: Hospitals were randomly assigned to either an innovative implementation strategy including a computerized decision support system (DSS) and professional audit and feedback or a minimal implementation strategy of audit and feedback only. Main outcome measures: Primary outcome measure was a combined rate of major maternal complications. Secondary outcome measures included process-related measures on guideline adherence, and patient-related outcomes. A process evaluation was performed alongside. Results: No statistically significant difference was found in both the occurrence of major complications and most secondary outcome measures between the two groups. Process evaluation showed limited use of the computerized DSS, with a large variation between hospitals (0–49,5% of the eligible patients), but positive experiences of actual users. Conclusion: Using a computerized DSS for implementation of the clinical guidelines for the management of hypertension in pregnancy did not result in fewer major maternal and fetal complications. Limited use of the DSS in the innovative strategy group could be an explanation for the lack of effect.