Factors explaining failure to suppress viral load in pregnant women living with HIV in Mbandaka, Equateur Province (Democratic Republic of Congo)

Introduction Mother-to-child transmission (MTCT) of HIV remains a persistent public health issue, especially in high-burden regions like sub-Saharan Africa. Suppressing maternal viral load through antiretroviral therapy (ART) is central to the prevention of vertical transmission. However, the effectiveness of this strategy is compromised by multiple factors. This study investigates the determinants of viral load suppression failure among pregnant women living with HIV in Mbandaka, Democratic Republic of the Congo, and explores their impact on MTCT risk. Purpose The primary aim is to identify the factors associated with virologic non-suppression in HIV-positive pregnant women and assess how these contribute to MTCT, thereby informing strategies to reduce perinatal HIV transmission. Methods A mixed-methods, longitudinal case-control design was adopted. The study population included 438 HIV-positive pregnant women, divided into 146 cases (non-suppressed viral load) and 292 controls (suppressed viral load). Data collection integrated retrospective chart reviews and prospective interviews. Statistical analysis, including logistic regression, was conducted using SPSS version 22.0. Results Key risk factors for virologic failure included poor adherence to ART (OR = 4.983; 95% CI [2.744–9.047]), previous ARV use (OR = 4.458; 95% CI [2.263–8.781]), and HIV-positive status at baseline (OR = 4.374; 95% CI [0.012–9.269]). Conversely, protective factors were prophylaxis initiation by the second month of pregnancy (OR = 0.446; 95% CI [0.202–0.983]), being married (OR = 0.298; 95% CI [0.126–0.705]), and symptomatic HIV status (OR = 0.057; 95% CI [0.012–9.269]). Conclusion Viral suppression failure in pregnant women is largely driven by modifiable factors such as treatment adherence and timing of prophylaxis. Strengthening adherence counselling, promoting early ART initiation, and enhancing social support systems—particularly through marital or community frameworks—are crucial for reducing MTCT. Routine viral load monitoring and personalised interventions remain key to improving outcomes. Further research is warranted to tailor ART delivery models to the socio-cultural context of Mbandaka and similar settings.