Social support is popularly regarded as a naturally existing resource that acts to prevent disorder by buffering the effects of stress or by meeting individuals' fundamental needs for meaningful human attachment. The present paper begins by discussing approaches to measuring social support that might be adopted in needs assessment research. A prospective study of 74 young mothers is described to illustrate the use of multiple measures of support in investigating their relationship to birth outcome measures. In this study, direct relationships were found between birth outcome indices and measures of both prenatal negative life events and psychological distress. Social support network size showed stress moderating effects when Apgar scores served as the outcome measure. When the presence of birth complications served as the criterion variable, moderating effects were also found for a support satisfaction measure. The paper closes by examining some implications of this study for needs assessments designed for the planning of preventive interventions.