BackgroundHypertensive disorders of pregnancy are among the leading causes of maternal mortality and morbidity in the U.S., with rates highest among birthing people who are Black, rural residents, and/or have low-income. Severe hypertension, in particular, increases risk of stroke and other serious pregnancy complications. To promote early detection and treatment of severe hypertension, the Alliance for Innovation on Maternal Health developed the Severe Hypertension During Pregnancy and Postpartum Period Safety Bundle (HTN Bundle). Multiple studies have demonstrated the HTN Bundle’s effectiveness in the inpatient setting. With funding from the National Heart, Lung, and Blood Institute, we engaged community partners to adapt the HTN Bundle for the outpatient setting (i.e., O-HTN Bundle) and planned for its implementation. In this paper, we describe the protocol for a study evaluating O-HTN Bundle implementation in 20 outpatient clinics serving Black, rural, and/or low-income populations.MethodsThis study is a hybrid type 3 effectiveness-implementation trial with a multiple baseline design. We will implement the O-HTN Bundle in three successive cohorts of clinics using a multicomponent implementation strategy to engage community partners (coalition, patient workgroup) and support clinics (training, facilitation, education materials, and simulations of severe hypertension events). To test the strategy, we will compare clinic fidelity to evidence-based guidelines for (a) patient education on hypertension and (b) blood pressure measurement technique, with repeated measures occurring before and after strategy receipt. We will also observe strategy effects on community- and clinic-level intermediate outcomes (community engagement, organizational readiness), implementation outcomes (reach, adoption, fidelity, maintenance), and effectiveness outcomes (receipt of guideline concordant care). Analyses will address whether outcomes are equitable across Black, rural, and/or low-income subgroups. Guided by the Consolidated Framework for Implementation Research 2.0, we will use mixed methods to identify adaptations and other determinants of implementation success.DiscussionThis study integrates community engagement and implementation science to promote equitable and timely response to severe HTN in the outpatient setting during pregnancy and postpartum. This is one of the first studies to implement an outpatient HTN Bundle and to use simulation as a strategy to reinforce team-based delivery of guideline concordant care.Trial registrationThis study was registered with ClinicalTrials.gov as “Testing Implementation Strategies to Support Clinic Fidelity to an Outpatient Hypertension Bundle (AC3HIEVE).” Registration number NCT06002165, August 21, 2023: https://clinicaltrials.gov/study/NCT06002165.