Several factors enhance the possibility of vertical HIV transmission in the pediatric population. Unfortunately, the data of the prevalence of HIV and associated risk factors in these populations remain limited in Rwanda. The study aimed to assess HIV prevalence and risk factors for infants born to mothers on ARV treatment at CHUB/Rwanda. MethodsA cross-sectional study was carried out on infants who were born to mothers under ARV treatment at CHUB. The associated risk factors were retrospectively assessed using prevention vertical HIV transmission records, and Dried Blood spots (DBS) were prospectively tested using Polymerase Chain Reaction (PCR). Data were analyzed by logistic regression. Ethical clearance (Ref: CMHS/IRB/198/2017) was issued by University of Rwanda to fulfill research ethical consideration.ResultsAmong 185(100%) infants born to HIV-positive mothers under ARV treatment, 5(2.7%) were HIV positive. The most associated risk factors were increased to over 1log copies/ml mother’s viral load (OR 9.3, 95% CI 1.01-85.45, P= 0.04) and mother’s CD4 count lower than 350 cells/µl (OR 6.4, 95% CI 1.03-40.06, P=0.04). The factors found to reduce the rate of vertical transmission of HIV were health facility as a delivery place (P=0.03), exclusive breastfeeding for 6 months (P= 0.006), and attending the antenatal care (P=0.01) while feeding children and vaginal delivery were associated risks but not statistically significant.ConclusionThe current study supports that the more mothers’ viral load and CD4 count decrease, so does the risk of HIV to their infants. A fact which indicates that both prevalence and risk factors remain an alarming issue. Much effort and multi-disciplinary approach are highly recommended.