This prospective study examined the effects of maternal characteristics, social support, and risk factors on infant-mother attachment in a heterogeneous sample. Two hundred and six women between the ages of 18 and 40 were interviewed during their last trimester of pregnancy and 1 year postpartum. Structural equation modeling revealed that maternal attachment experiences were significantly related to prenatal representations of the infant and of the self as a mother, which were significantly related to infant-mother attachment assessed by the Strange Situation. Maternal risk factors were significantly related to prenatal representations, and social support from other women predicted infant-mother attachment. The overall model indicated a good fit. Thus, both individual and contextual factors were important in explaining infant attachment security.