ABSTRACT: Preterm birth is the major cause of perinatal mortality and morbidity. This tragic outcome occurs most frequently among mothers of lower social class and those with few psychosocial resources, including social support. Intervention studies supplying social support in other health fields have demonstrated improved psychosocial and behavioral outcomes, but not physical outcomes. This is a review of the current information about such effects and a description of studies that are attempting to test the effect of supplemental social support in pregnancy on physical outcomes such as preterm birth.