This special issue of Pediatrics honors the critical role that mothers play in their child’s health during 3 important periods: preconception, prenatal, and early childhood. Two general public heath messages are highlighted by the researchers who explored maternal influences during the preconception period: the ongoing challenge of pregnancy-related health promotion among all women of childbearing age, and the implications of increased use of reproductive technology. In studies of the prenatal period, researchers focused on maternal influences such as healthy prenatal behavior and testing for diseases that can be transmitted perinatally. In studies of the early childhood period, researchers focused on what mothers can do to keep infants and young children safe and healthy, including accessing health care and creating a safe and healthy environment at home. Findings in this supplement are based on premier national data sets, including comprehensive health surveys such as the National Health and Nutrition Examination Survey and the Behavioral Risk Factor Surveillance System, specialized national surveys such as the National Immunization Survey and the Pregnancy Risk Assessment Monitoring System, and national vital statistics data. Also included are findings from a variety of state and local one-time and ongoing projects.In examining on ways that mothers influence the health of their infants and young children, we link 2 key areas of medicine—obstetrics and pediatrics—which have similar objectives but often work independently of each other. We also link numerous content areas and disciplines of public health research that frequently have little collaboration and interdisciplinary discussion, including immunization, birth defects, developmental disabilities, reproductive health, human immunodeficiency virus/acquired immune deficiency syndrome, injury control, chronic disease, nutrition, health education, and psychology. While it may be convenient for operational purposes to divide health care and health research into ever-smaller units, we must remember to step back periodically and examine how these areas tie together—how they influence each other, and ultimately how they influence child health.Physicians and other health care workers know well the role they play in their own field of expertise, but may not always realize the opportunity they have to improve health beyond that scope. For example, in an obstetric practice for example, staff have the opportunity to talk with expectant mothers about the health and safety of their future newborns; preparing a safe home environment; infant’s health care in the hospital, including vaccinations and newborn hearing screening; and breastfeeding. Pediatric health care workers, likewise, could discuss issues such as pregnancy planning and the importance of taking folic acid with women before they become pregnant, as no one is more likely to become pregnant than a woman who has young children.As with physicians and health care workers, public health researchers must take advantage of opportunities to integrate methods and findings to ensure that their research is responsive to public health needs and that the implications for health care are clear. With this in mind, public health researchers throughout the Centers for Disease Control and Prevention—and our research partners throughout the United States—were asked to submit articles for this issue.While “maternal influences on child health” brings together research from many different fields, this topic is itself part of a larger picture. Mothers certainly are not the only influence on their children’s health. Fathers, families, friends, physicians, health care workers, teachers, and other community members all have an opportunity to play a role, either directly or indirectly, in the health and well-being of young children. From the point of view of the child, the preconception, prenatal, and early childhood periods focused on in this issue are just the beginning of mothers’ influence, which continues throughout their lives. And while we have focused on the health of children, the maternal/infant relationship can also have a positive impact on mothers’ health. During pregnancy, women are often more health-conscious than usual and receptive to advice from physicians and others. Pregnancy can be a unique opportunity to encourage women to make lasting changes—taking multivitamins, being tested for human immunodeficiency virus, quitting smoking and binge drinking, eating nutritiously, etc—that will improve not only the health of her child, but her own health as well. In the broadest sense, promoting health is just a part of improving the total well-being of individuals, families, and ultimately of society.We hope that this issue will encourage you to step back and search for critical links between your field and others. Building and strengthening these linkages will enable health care providers and researchers to make increasingly practical and valuable contributions to the public’s health. In closing, we would like to wish a “Happy Mothers’ Day” to all those who work to promote the health of mothers and their children.