Although recent theoretical work points to the multidimensional character of acculturation, empirical studies often fail to operationalize the concept in ways that capture the complexity. This study uses data from indepth interviews with 58 pregnant and recently postpartum women of Mexican descent to demonstrate that prior studies examining acculturation and low birth weight have focused too much on negative health behaviors and too little on social support and access to resources. The analysis also demonstrates the importance of examining social change in sending and receiving communities by addressing the starting point for acculturation and the forces for acculturation in immigrants' lives.