Globally, the proportions of women of reproductive age living with HIV vary between regions, with significantly higher proportions in sub-Saharan Africa. The scale-up of multiple-drug antiretroviral therapy in Africa has changed childbearing dynamics for HIV-positive women, with an impact on pregnancy incidence, although there is little understanding of the factors associated with pregnancy incidence among these women. This descriptive cross-sectional study investigated the incidence of pregnancy among HIV positive women in Rangwe Sub-County, and identified the associated personal, medical and community factors, using semi-structured questionnaires administered to 244 women on antiretroviral therapy. Quantitative data was analyzed using descriptive statistics and logistic regression using SPSS v.23 (a=0.05), while qualitative data was subjected to thematic analysis. Over 95% of the women had conceived after being diagnosed HIV positive. Age, marital status and CD4 cell count were significantly associated with pregnancy incidence (p<0.05). Partner consent (p=0.034), and partner HIV serostatus (p=0.005) were significantly associated with pregnancy, unlike partner support, partner awareness of participant’s status, defaulting from ARVs, and community or family acceptance of childbearing (p>0.05). Women with undetectable viral load (HIV RNA <50 copies/mL) were 2.7 times more likely to get pregnant compared to women with detectable viral load (OR=2.71; 95%CI=1.8-3.22; p=0.028). The Ministry of Health and relevant stakeholders should improve on the strategies to enhance viral load and CD4 cell count monitoring, HIV status disclosure between sexual partners, and adoption of strategies that promote male partner support to women to get pregnant, and to use family planning methods of choice.