Infant and child mortality rates are significantly lower in the Maternal and Child Health-Family Planning (MCH-FP) area of Matlab, Bangladesh, than in a comparison area. The two areas are similar in terms of socioeconomic characteristics, but the MCH-FP area provides better maternal and child health and family planning services, resulting in different reproductive patterns, including lower fertility rates and longer intervals between pregnancies. We use data from the Matlab Demographic Surveillance System for nearly 126,000 singleton live births that occurred between 1982 and 2002 to investigate the extent to which the different reproductive patterns in the MCH-FP area explain why infant and child mortality rates are lower there. Differences in reproductive patterns account for a small portion (up to 20 percent) of the variation in these rates between the MCH-FP and comparison areas, suggesting that the majority of the difference is due to the quality of MCH services.