Despite several sociocultural factors associated with increased risk for low birth weight and infant mortality, the rate for infants born to first-generation and less acculturated Mexican immigrant women is the same as that of non-Hispanic whites, and half that of African Americans with similar risks. It appears that sociocultural rather than genetic variables are the primary factors associated with this phenomenon. Higher levels of acculturation to North American values and lifestyle in Mexican American childbearing women have been correlated with poor perinatal outcomes, including low birth weight. Acculturation is emerging as an important variable that should be considered when providing health care to Mexican immigrant childbearing women and their families.