Health care personnel are exposed to infectious diseases in the community as well as in the health care setting when they care for patients with transmissible conditions. Pregnant nurses, physicians and others face an additional risk--that of exposing their unborn children to some of these infections. Risk factors vary greatly between diseases and it is, therefore, important that each be evaluated and acted upon realistically. We will discuss and compare the risk of infections such as hepatitis, cytomegalovirus, tuberculosis, chickenpox, and others. With this knowledge, administrators and personnel involved will be able to make decisions about which patients should not be cared for by pregnant personnel, and which areas pose too high a risk for the mother and child so that a temporary transfer may be advisable. We address the multiplicity of preventive measures available for the prevention of maternal infections.