Purpose: This research examined low-income, urban mothers' social support environments as predictors of depressive symptoms from late pregnancy through six months postpartum.

Background: The lack of a supportive social environment has been shown to increase risk for women's depressive symptoms during pregnancy and postpartum, with serious potential outcomes for women and their children. The mechanisms of effect for social support remain unclear, though a buffering (moderating) effect has been theorized.

Methods: A longitudinal design was used for secondary analysis of data for 279 low-income women of Mexican American or African American ethnicity. Data had been collected for a previous, randomized trial of a home-visit intervention program. The theoretical model incorporated social environmental factors and guided hierarchical linear multiple regression analyses to predict depressive symptoms.

Results: In this sample, 33% at pregnancy, and 21% at 2 and 6 months postpartum reported severe symptoms. The final predictive model showed that depression at pregnancy and at 2 months postpartum, and perceived social support were strong predictors of depressive symptoms at 6 months postpartum. Social integration at pregnancy, network size, stability of support from the father of the baby, and difficult life circumstances also were significant predictors of symptoms at 6 months. Demographic factors were not predictive. The final model predicted 56% of the variance in women's symptoms. The buffering effects of social support for the effects of life difficulties were not significant at any time point.

Conclusions: A substantial proportion of low-income women had severe depressive symptoms during pregnancy compared to postpartum. Stable support from the father of the baby can be a protective factor. Perceived social support had a direct effect on women's postpartum symptoms.