Objectives Group prenatal care (GPC), an alternative to individual prenatal care (IPC), is becoming more prevalent. This study aimed to describe the attendance and reasons of low attendance among pregnant women who were randomly assigned to receive GPC or IPC and explore the maternal characteristics associated with low-attendance. Methods This study was a descriptive study among Medically low risk pregnant women (N = 992) who were enrolled in an ongoing prospective study. Women were randomly assigned to receive CenteringPregnany GPC (N = 498) or IPC (N = 994) in a single clinical site The attendance frequency and reason for low-attendance (i.e. ≤ 5/10 sessions in GPC or ≤ 5 visits in IPC) were described separately in GPC and IPC. Multivariable logistic regressions were performed to explore the associations between maternal characteristics and low-attendance. Results On average, women in GPC attended 5.32 (3.50) sessions, with only 6.67% attending all 10 sessions. Low-attendance rate was 34.25% in GPC and 10.09% in IPC. The primary reasons for low-attendance were scheduling barriers (23.19%) and not liking GPC (16.43%) in GPC but leaving the practice (34.04%) in IPC. In multivariable analysis, lower perceived family support (P = 0.01) was positively associated with low-attendance in GPC, while smoking in early pregnancy was negatively associated low-attendance (P = 0.02) in IPC. Conclusions for Practice Scheduling challenges and preference for non-group settings were the top reasons for low-attendance in GPC. Changes may need to be made to the current GPC model in order to add flexibility to accommodate women's schedules and ensure adequate participation. Trial registration NCT02640638 Date Registered: 12/20/2015.