This prospective study examined the effects of prenatal social support on maternal and infant health and well-being in a sample of low-income pregnant women (N = 129). Three aspects of support (amount received, quality of support received, and network resources) and four outcomes (birth weight, Apgar scores, labor progress, and postpartum depression) were studied. Results indicated that women who received more support had better labor progress and babies with higher Apgar scores. Women with higher quality support had babies with higher Apgar scores and experienced less postpartum depression. Also, women with larger networks had babies of higher birth weight. Further analyses indicated that the outcomes as a whole were more consistently predicted by instrumental rather than emotional forms of support. Finally, although there was some evidence for stress-buffering effects of support, the overall findings were more consistent with a main effect model.