It is estimated that 4 million children die each year of vaccine- preventable diseases and another 4 million are permanently disabled. Although vaccination is the most cost-effective health method, there is a discrepancy between our level of knowledge and practices applied. Vaccination of pregnant women provides the mother with antibodies that could be transferred across the placenta and provide the neonate with high antibody titers until active immunization is likely to be protective. The ability to provide such passive childhood immunization is beneficial and cost-effective, especially in developing countries where routine childhood immunization is not widely practiced. Further progress depends on the development of more efficient antigens, carrier proteins, and formulations of multiple-antigen vaccines. Future studies should determine the ideal timing for in utero vaccination to provide protective antibodies to the full-term infant and the premature infant. This ideally should be achieved without compromising the protective effect during the first months of life and without causing immune tolerance when given early in pregnancy. The future of in utero vaccination depends on continuing basic research, which should provide improved vaccines and clinical studies that demonstrate the safety and effectiveness of vaccination for both mothers and infants. Liability issues should be addressed and greater awareness of obstetricians, family physicians, and the general public should be achieved.