Most countries in Latin America have completed or are approaching the completion of the fertility transition. Yet, the pace of the fertility decline in the region is characterized by vast inequalities. There are considerable cross-country and within-country differences, and women in lower socioeconomic strata continue to be more at risk of high adolescent and total fertility. This dissertation investigates reproductive health disparities in four Central American countries, Paraguay, and Argentina. Using Demographic and Reproductive Health Surveys, as well as a unique longitudinal dataset from Northern Argentina, I employ logistic regression, event history analysis, and logistic random effects techniques to examine the factors related to disparities in out-of-union childbearing, sexual behaviors in the transition to adulthood, and contraceptive use among indigenous women. I find that young age, residence in the capital region, and higher levels of religiosity and wealth are significantly related to out-of-union fertility in Paraguay. In Central America, age distributions for important events during the transition to adulthood have undergone little to no change over the past two decades. School enrollment significantly decreased the hazard of experiencing sexual initiation, first marriage and first birth in all countries. Finally, I find unequivocal evidence for the increased uptake of modern contraception among indigenous Toba women in Namqom, Argentina, following the passage of a 2002 law lifting financial barriers to contraception in that country. In addition, I find decreased use among women who have migrated to Namqom from more remote regions of Northern Argentina, and increased use among women with relatively early ages at menarche. Further investigation utilizing the sequencing techniques employed by those researching transitions to adulthood in the developed world is needed to examine the changing adolescent experience in Latin American countries. Moreover, a focus on cross-ethnic variation in health disparities that highlights the experiences of indigenous groups throughout the region is needed to determine how we may improve access to and acceptability of modern reproductive health services.