This study explores the effects of imbalances in the sex ratio on both the quantity and the quality of children, with a focus on changes in intra-household bargaining power. We first present a theoretical model of intra-household bargaining in the presence of conflicting family goals within a couple, and show that male scarcity (a decrease in the male-to-female sex ratio) induces an increase in the number of children and a decrease in the quality of children. Second, using the impact of World War II on the sex ratio as a quasi-natural experiment, we establish empirically that the decrease in the male-to-female sex ratio in World War II contributed to a smaller decline in fertility and child mortality rates in postwar Japan. In particular, the fertility rate would have fallen by an additional 12% and the child mortality rate by an additional 13% between 1948 and 1970 absent the decrease in the sex ratio.