Unraveling a Public Health Enigma: Why Do Immigrants Experience Superior Perinatal Health Outcomes?

Research has pointed to an apparent public health enigma among new immigrants to the United States: high-risk groups, particularly low-income immigrants from Mexico and Southeast Asia, show unexpectedly favorable perinatal outcomes and seem to be “superior health achievers.” This study attempts to unravel the reasons for this “epidemiological paradox” by examining an in-depth data set drawn from a Comprehensive Perinatal Program (CPP) in San Diego County providing prenatal care services to low-income pregnant women, most of whom were immigrants from Mexico and various Asian countries, The CPP data set consists of nearly 500 independent variables per case (including most of those listed in the research literature as likely biomedical and sociocultural determinants of pregnancy outcomes) for a sample of both foreign-born and U.S.-born women, matched to infant health outcome measures collected from hospital records for every baby delivered by CPP mothers during 1989-1991. The analysis focuses on the identification of maternal risk factors that best explain observed ethnic and/or nativity differences in pregnancy outcomes (birth weight, diagnoses at birth, complications, length of hospitalization of the baby). Asians and Hispanics (mostly foreign-born) had superior outcomes relative to Anglos and African-Americans (mostly native-born); within ethnic groups outcomes were generally better for immigrants than for natives; and for immigrants outcomes worsened as the general acculturation or “Americanization” of the mother increased. The comparative socioeconomic advantages of US-born women – in education, employment, income, English literacy and proficiency – appeared to be overwhelmed by biomedical, nutritional and psychosocial disadvantages. In multivariate analyses, ten independent variables – a set of both biomedical and sociocultural factors – remained as significant predictors of pregnancy outcomes. Four qualitative case histories of CPP mothers are drawn from psychosocial reports to shed further light on the quantitative findings drawn from the statistical analysis. Limitations and implications of this study for health policy and future research are considered