Background: Prevention of both school dropout and teen pregnancy represent clear public health priorities for South Africa, yet their complex and potentially cyclical relationship has not been fully explored. Objective: To further understand how this relationship operates, we analyzed data from a randomized trial of young women aged 13 to 20 years enrolled in school in rural South Africa to estimate the association between pregnancy and subsequent dropout and between dropout and subsequent pregnancy. Method: We examined inverse probability (IP) of exposure-weighted survival curves for school dropout by pregnancy and for pregnancy by school dropout. We used weighted curves to calculate 1-, 2-, and 3-year risk differences and risk ratios. Additionally, we used an IP-weighted marginal structural cox model to estimate a hazard ratio (HR) for each relationship. Results: Dropout from school was associated with subsequent pregnancy (HR 3.58; 95% confidence interval [CI] [2.04, 6.28]) and pregnancy was associated with subsequent school dropout (HR 2.36; 95% CI [1.29, 4.31]). Young women who attended school but attended fewer days had a higher hazard of pregnancy than those who attended more school (HR 3.64; 95% CI [2.27, 5.84]). Conclusion: Pregnancy is both a cause and a consequence of school dropout. Consideration of school attendance and academic performance could ultimately enhance pregnancy prevention efforts in this population. Programs should be tailored differently for (1) girls who have dropped out of school, (2) those who are in school and at risk for pregnancy, and (3) those who are in school and become pregnant.