Background. This study examines whether the relationship between maternal stress or abuse situations and infant birth weight differs between homeless and non-homeless women. Methods. Analyses are based on data from the Pregnancy Risk Assessment Monitoring System (PRAMS), [2002][2003][2004][2005][2006][2007]. Results. Homeless women were significantly more likely to experience stressful life events, abusive situations, and poor maternal health than non-homeless women during pregnancy. Birth weight among infants of homeless women was, on average, 17.4 grams lighter than for infants of non-homeless women, after adjusting for maternal age, race, ethnicity, region, education, and marital status. The impact of maternal health, stress, and abuse variables on pregnancy and infant birth weight significantly interacted with homeless status. For example, vaginal bleeding, nausea, kidney/bladder infection, and failure to receive early prenatal care had significantly larger negative impacts on birth weight among homeless women than non-homeless women. Infant birth weight was consistently lower among homeless women, more so when maternal stress and abuse were involved, across all classifications of their prepregnancy weight. Conclusion. Stress and abusive situations among pregnant women have a negative influence on pregnancy-related conditions and infant birth weight. However, this negative influence is even more pronounced among homeless women.