Challenges of teenage pregnancy and adverse outcomes of pregnancy constitute a major public health problem in South African women of the childbearing age of 15 to 49 years. This is a 6-year long study that was conducted in Pretoria, South Africa in order to identify factors that affect utilization of modern contraceptives and adverse pregnancy outcomes in women of the childbearing age of 15 to 49 years. Data analysis was conducted by using two-by-two Pearson’s chisquare tests of associations, binary logistic regression analysis, survival analysis, and multilevel analysis. The study showed that the percentage of women who regularly used modern family planning methods such as condoms, pills, injections, intra-uterine devices and sterilization was 41.74%. The average ages of women at first sex and pregnancy were 18.72 and 19.36 years respectively. Adverse outcomes of pregnancy occurred in 12.19% of women. Based on Odds Ratios (OR) estimated from binary logistic regression analysis, utilization of contraceptives was significantly influenced by easy access to family planning services, level of support from sexual partner, and young age at first pregnancy. Based on Hazard Ratios (HR) estimated from the Cox Proportional Hazards Model, the occurrence of adverse outcomes of pregnancy was significantly influenced by easy access to family planning services, unwanted pregnancy, and young age at first pregnancy. Women who experienced adverse outcomes of pregnancy were characterized by poor utilization of reproductive health and modern family planning services. There was a significant difference among the 20 health service delivery wards and 11 health service facilities in which reproductive health services were delivered to women with regards to the quality of service delivery.