摘要：Objectives. I sought to identify whether there were associations between paternal race/ethnicity and birth outcomes among infants with parents of same- and mixed-races/ethnicities. Methods. Using the National Center for Health Statistics 2001 linked birth and infant death file, I compared birth outcomes of infants of White mothers and fathers of different races/ethnicities by matching and weighting racial/ethnic groups following a propensity scoring approach so other characteristics were distributed identically. I applied the same analysis to infants of Black parents and infants with a Black mother and White father. Results. Variation in risk factors and outcomes was found in infants of White mothers by paternal race/ethnicity. After propensity score weighting, the disparities in outcomes by paternal or parental race/ethnicity could be largely attributed to nonracial parental characteristics. Infants whose paternal race/ethnicity was unreported on their birth certificates had the worst outcomes. Conclusions. The use of maternal race/ethnicity to refer to infant race/ethnicity in research is problematic. The effects of maternal race/ethnicity on birth outcomes are estimated to be much larger than that of paternal race/ethnicity after I controlled for all covariates. Not listing a father on the birth certificate had a strong association with outcomes, which might be a source of bias in existing data and a marker for identifying infants at risk. Despite great improvement in birth outcomes in the United States, significant and continuing differences persist across racial and ethnic groups. The low-birthweight (LBW; defined as a birthweight less than 2500 g) rate of non-Hispanic Black infants has been steadily nearly double that of non-Hispanic White infants. 1 , 2 Therefore, Black mothers are usually the focus of birth-outcome disparity research and policy, whereas White mothers are regarded to be at a lower risk. These disparities are believed to result from complex interactions among genetic variations, social and environmental factors, and specific health behaviors. 3 – 5 Most previous research, when referring to an infant's race/ethnicity, used maternal race/ethnicity instead of infant race/ethnicity both because the child's race may not be clear in the case of mixed race and because the mother's race/ethnicity is thought to have more influence on birthweight than the father's race/ethnicity. 6 Furthermore, the father's information is often not available in the data sets of choice. This common practice might be a serious analytic shortcoming because it overlooks the father's race/ethnicity and it treats infants of mixed-race parents and those of same-race parents equally. Furthermore, even when the father's race/ethnicity is available and included as an indicator variable, most models don’t allow coefficients of covariates to differentiate between groups, which implicitly assumes no other difference between parents of mixed- and same-race/ethnicity except for their race/ethnicity. Many studies have shown different patterns in socioeconomic characteristics between intermarriage and endogamous marriage in the United States. On the basis of 1990 US census data, Fu found that Black or Mexican American husbands’ White wives had less schooling than did the White wives of White husbands. 7 Fu explained this pattern by using both the status exchange and in-group preference hypotheses. Status exchange hypothesizes that in a marriage market framework, minority men marry less-desired White women (e.g., of lower education) in exchange for higher social status. The second hypothesis, in-group preference, simply suggests that people prefer members from their own group, and thus, intermarriage is the less desirable scenario. According to the National Center for Health Statistics (NCHS) natality files, between 1968 and 1996, the proportion of infants born to 1 Black and 1 White parent increased gradually from 0.33% to 1.77%, and the proportion of infants born to 1 Asian/Pacific Islander parent and 1 White parent also increased substantially, from 0.25% to 1.21%. 8 These mixed-race infants provide a unique chance to investigate associations between both maternal and paternal race/ethnicity and infant outcomes. To date, only a few studies have examined birth outcomes of interracial infants, and all of these studies focused on Black and White mixed-race infants. Together they found that mixed-race couples differed significantly with respect to their sociodemographic characteristics from the endogamous couples. After control for those variables, biracial infants were found to have worse birth outcomes than infants with 2 White parents but better than infants with 2 Black parents. 6 , 8 – 12 (Henceforth, infant's race/ethnicity will be referred to by the notation “maternal race/ethnicity–paternal race/ethnicity” [e.g., White–Black].) However, these studies have several limitations. First, they didn't examine groups other than Black and White race. Second, paternal information is often missing from natality data, especially for infants of Black mothers. Although these infants are more likely to have adverse birth outcomes, 10 – 13 they are often omitted from studies. Third, none of these studies examined Apgar score (a routine evaluation of the general physical condition of the newborn usually performed at 1 and 5 minutes after delivery) as a birth outcome, although it has been repeatedly found to have strong predictive power for infant mortality. 14 , 15 In terms of method, previous studies used multivariate regressions or logistic models with a categorical variable of race combinations. A potential concern regarding this approach is that it assumes covariates have the same effects (coefficients) on outcomes of interest across all racial combinations. I investigated differences in birth outcomes (i.e., birthweight, LBW rate, 5-minute Apgar score, and infant mortality) for infants born to non-Hispanic White mothers and non-Hispanic Black fathers (henceforth, White and Black refer to non-Hispanic White and non-Hispanic Black) and those born to White mothers and fathers of 6 other selected racial/ethnic groups. I hypothesized that paternal race/ethnicity might affect birth outcome, but this influence would be smaller than that of maternal race/ethnicity because mothers play a more important role than fathers in the course of pregnancy and delivery.
