Background Of 270,000 new HIV infections in children, 90% are in Sub-Saharan Africa. High fertility levels and high number of women infected with HIV results in high rates of Mother-to-Child-Transmission (MTCT) in SSA. To date, most efforts to prevent MTCT of HIV have focused on the third prong, a strategy that offers ARV drugs to HIV infected pregnant women and their exposed infants. However, the effective use of contraceptives to prevent unwanted pregnancies among HIV-positive women has the ability to reduce the rates of MTCT of HIV at a lower cost compared to the third prong. There is limited information on the levels of contraceptive use and associated factors among HIV positive women in Northern Tanzania.

Methods This was a cross-sectional study conducted in February–May 2014 in three randomly selected districts of Kilimanjaro region. Univariate and multivariate logistic regression analysis were used to describe data and determine independent predictors of modern contraceptives use respectively.

Results Of the 672 HIV-positive women participated in this study, 93% were aware of modern contraceptive methods, 54% were current modern contraceptives users and 21% were using dual contraceptive methods. Commonly modern contraceptives method used included male condom (41%), Depo-Provera (13%) and oral contraceptive pills (10%). Modern contraceptive use was significantly higher among HIV-positive women with; secondary education (aOR = 3.6, 95% CI 1.4–9.5), who do not plan to have more children (aOR = 2.2, 95% CI 1.5–3.2), counselled on contraceptives at CTC (aOR = 3.7, 95% CI 2.7–5.1), disclosed their HIV status to their partner (aOR = 2.5, 95% CI 1.8–3.4).

Conclusions Prevalence of modern contraceptive use was higher than the national level. 46% of HIV-positive women are not using any method of contraception despite being sexually active. Strategies are required to increase use of long-term contraceptive methods to those who do not want more children and strengthening counselling to target non-users.