Background: CenteringPregnancy is an innovative model of group prenatal care (GPNC) that can improve pregnancy outcomes and experiences of care. Yet, because CenteringPregnancy requires significant adaptations in settings designed for individual care, GPNC can be difficult to implement with fidelity. Purpose: This research describes circumstances in 2 clinics and in pregnant women's personal lives related to GPNC, and group leader responses to these circumstances. Methods: Data were gathered through participant-observation of 4 GPNC series, and 54 semi-structured interviews of 21 pregnant women and 2 group leaders. Participants were predominantly African-American or Hispanic. The approach, Interpretive Description, was informed by Situational Analysis. Results: Women's personal lives and clinic settings had profound effects on providing GPNC. Many women had limited social support, severe financial stress, and challenges accessing care. Furthermore, clinics did not provide full resources for GPNC; consequently, recruitment procedures, space, staffing, and materials were sometimes inadequate. Group leaders, who viewed GPNC as providing important benefits for their patients, found themselves “in a hard spot,” struggling to balance model fidelity with these limitations. Strategies they developed included advocating, improvising, compromising, and modifying the CenteringPregnancy model. Conclusions: Limited resources and modifications affected women's experience of GPNC, group stability, and group leader experience. Future research should explore variations of GPNC used across settings, and the impact of variations on outcomes, experience of GPNC, and sustainability of the model. Funding: The project described was funded in part by the National Institute of Nursing Research, T32NR008346 and F31NR00991, the March of Dimes, Sigma Theta Tau Delta Mu Chapter, and the Yale Evelyn Anderson Research Fund. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institute of Nursing Research.