Summary group characteristics for PrIMA restricted randomisation
| Group | County | County HIV prevalence, 201616 (%) | No. of facilities | Mean ANC Volume (SD) | Group description |
| 1 | Homa Bay | 26.0 | 2 | 173 (60.8) | High volume |
| 2 | Homa Bay | 26.0 | 4 | 59.8 (1.3) | Medium volume |
| 3 | Homa Bay | 26.0 | 4 | 53.8 (3.3) | Low volume |
| 4 | Siaya | 24.8 | 2 | 140 (26.9) | High volume |
| 5 | Siaya | 24.8 | 4 | 54.8 (6.4) | Medium volume |
| 6 | Siaya | 24.8 | 4 | 38 (5.5) | Low volume |
ANC, antenatal care; PrEP, pre-exposure prophylaxis; PrIMA, PrEP Implementation for Mothers in Antenatal Care.