This cluster-randomized study aimed to assess the Elombe (“Champion”) standard operating procedure (SOP), implemented by providers and Mentor Mothers, on HIV-positive pregnant women’s retention between first and second antenatal visits. Sixteen facilities in Kinshasa were randomly assigned to intervention (SOP) or comparison (no SOP). Effect of the SOP was estimated using relative risk. Women in comparison facilities were more likely to miss second visits (RR 2.5, 95% CI 1.05–5.98) than women in intervention facilities (30.0%, n = 27 vs. 12.0%, n = 9, p < 0.002). Findings demonstrate that a simple intervention can reduce critical early loss to care in PMTCT programs providing universal, lifelong treatment.