OBJETIVO: Identificar a taxa de transmiss o vertical do HIV e avaliar os fatores envolvidos em partes materna e fetal. MéTODOS: Estudo transversal realizado no Servi o de Atendimento Especializado. Foram investigados 102 prontuários de mulheres com HIV que deram à luz a recém-nascidos vivos. RESULTADOS: A prevalência de 6,6% de transmiss o vertical. Entre as crian as infectadas: 40,0% de m es sem pré-natal e 75% sem a profilaxia com anti-retrovirais durante o pré-natal, 50,0% sem profilaxia com AZT com oral e amamentado. Entre as crian as n o infectadas: 91,5% iniciaram a profilaxia com AZT oral ao nascimento e 84,1% das m es receberam ARV. CONCLUS O: A ocorrência de transmiss o vertical do HIV no servi o de referência correspondeu a 6,6%, o que indica uma alta prevalência. OBJECTIVE: To identify the rate of vertical transmission of HIV and assess the factors involved in maternal and fetal share. METHODS: Cross-sectional study conducted in the Specialized Care Service. We investigated 102 clinical records of HIV positive women who had given birth to live newborns. The primary variable was the occurrence of vertical transmission of HIV and the secondary variables were the factors associated with vertical transmission of HIV. RESULTS: Prevalence of 6.6% of vertical transmission. Among the infected children: 40.0% of mothers with out prenatal care and 75% without prophylaxis with antiretroviral drugs during the prenatal, 50.0% without AZT prophylaxis with oral and breast-fed. Among the uninfected children: 91.5% were started on prophylaxis with oral AZT at birth and 84.1% of mothers received ARV delivery. CONCLUSION: The occurrence of vertical transmission of HIV in the reference service corresponded to 6.6%, indicating a high prevalence.