Despite the pervasiveness of child marriage and its potentially adverse consequences on reproductive health outcomes, there is relatively little empirical evidence available on this issue, which has hindered efforts to improve the targeting of adolescent health programs. The purpose of this study was to assess the association of child marriage with fertility, fertility control, and maternal health care use outcomes in four South Asian countries: India, Bangladesh, Nepal, and Pakistan. Data for the study come from the most recent Demographic and Health Surveys conducted in the study countries; we used a subsample of women aged 20-24 years. Child marriage, defined as first marriage before 18 years of age, is categorized into two groups: first married at ages 15-17 years and first married at age ≤14 years. We used multivariate logistic regression models. The results of the study suggest that child marriage is significantly associated with a history of rapid repeat childbirth, current modern contraceptive use, female sterilization, not using contraception before first childbirth, pregnancy termination, unintended pregnancy, and inadequate use of maternal health services, although the associations are not always consistent across countries. Furthermore, women who married in early adolescence or childhood show a higher propensity toward most of the negative outcomes, compared with women who married in middle adolescence. Child marriage adds a layer of vulnerability to women that leads to poor fertility control and fertility-related outcomes, and low maternal health care use. Copyright © 2013 Society for Adolescent Health and Medicine. Published by Elsevier Inc. All rights reserved.