Research has shown that health outcomes for urban women of Mexican descent are related to acculturation. The purpose of this research was to compare perinatal outcomes of 773 women of Mexican descent who gave birth in three rural northern California hospitals, in relation to acculturation measured three different ways: by place of birth, by language spoken, and by the two factors combined as an Acculturation Index (AI). The prenatal and birth records of 773 Mexico-born or U.S.-born women of Mexican descent were reviewed. Results showed that language spoken was a less useful indicator of acculturation associated with perinatal complications than place of birth or the AI. The categorization of acculturation with the AI enhanced understanding of more specific groups of rural women and their particular health outcomes.