Perinatal outcomes in two dissimilar immigrant populations in the United States: a dual epidemiologic paradox

Previous studies have addressed perinatal outcomes in Hispanic, black, and white non-Hispanic women and demonstrated that although foreign-born Mexican American women have many demographic and socioeconomic risk factors, their rates of low birth weight (LBW) infants and infant mortality are similar to those of white women. This phenomenon has been termed an epidemiologic paradox. There have been no population-based studies on women of Asian Indian origin, a relatively new, highly educated, and affluent immigrant group that has been reported to have a high rate of LBW infants. The objective of this study was to define the sociodemographic risk profile and perinatal outcomes in women of Asian Indian birth and to compare these outcomes to foreign-born Mexican American and US-born black and white women.

The vital records for self-reported foreign-born Asian Indian (0.8%) and Mexican women (26.7%) and US-born black (31.2%) and white women (31.2%) were extracted from California's 1 622 324 births, 1995-1997. Sociodemographic risk profiles; the percentage of LBW, very low birth weight (VLBW), prematurity, and intrauterine growth retardation (less than third percentile); and percentage of fetal, neonatal, and postneonatal death rates were compared. Logistic models were used to estimate the importance of selected sociodemographic and medical factors to the prediction of LBW infants in each racial/ethnic group.

When compared with whites, US-born blacks and foreign-born Mexican mothers were at increased risk for adverse perinatal outcomes on the basis of higher levels of inadequate prenatal care, teen births, Medi-Cal paid delivery, and lower levels of maternal and paternal education. Foreign-born Asian Indian mothers had good prenatal care, were rarely teenagers, had dramatically higher levels of both maternal and paternal education, and had the lowest percentage of deliveries paid for by Medi-Cal. Black infants had the highest rates of prematurity; intrauterine growth retardation; LBW; and fetal, neonatal, and postneonatal mortality. Paradoxically, despite their high-risk profile, Mexicans did not have elevated levels of LBW or neonatal mortality. Conversely, Asian Indian infants, although seemingly of low sociodemographic risk, had high levels of LBW, growth retardation, and fetal mortality. Logistic regression analysis of independent risk factors for giving birth to an LBW infant showed higher maternal education, early access to prenatal care, and having private insurance to be protective in white non-Hispanic and black but not in Asian Indian and Mexican-born women.

Despite their high socioeconomic status and early entry into care, foreign-born Asian Indian women have a paradoxically higher incidence of LBW infants and fetal deaths when compared with US-born whites. Factors that protect from giving birth to an LBW infant in white women were not protective among Asian Indian women. Current knowledge regarding factors that confer a perinatal advantage or disadvantage is unable to explain this new epidemiologic paradox. These findings highlight the need for additional research into both epidemiologic and biological risk factors that determine perinatal outcomes.