BELLEVUE, WASH. – Hispanic women are much more likely than white women to give birth to an infant with small or no ears, an analysis of data from the National Birth Defects Prevention Study found.
In the NBDPS study of more than 8,500 births in the United States, the incidence of congenital isolated anotia or microtia was about three times higher among U.S.-born Hispanic women and five times higher among foreign-born Hispanic women, compared with non-Hispanic white women.
The elevation of risk for Hispanic women was especially pronounced if they had not completed high school, were obese, or smoked around the time of conception, and if they were less acculturated to the U.S. lifestyle.
"Anotia/microtia represents an extreme example of a racial/ethnic disparity in birth defects, especially among Hispanics," commented lead investigator Adrienne T. Hoyt, an epidemiologist with the Texas Department of State Health Services in Austin.
"These differences may be due to a combination of environmental, cultural, and genetic factors, which I think point a way toward future research in this area," she added at the annual meeting of the Teratology Society.
Session attendee Dr. Jan M. Friedman, a medical geneticist at the University of British Columbia in Vancouver, commented, "I’m having a hard time trying to get my head around how these factors are related to microtia/anotia if it isn’t poverty. Do you think they could all be just surrogates for poverty? [Lack of money] obviously has an influence on diet, access to medical care, and many other things."
Session cochair Suzan L. Carmichael, Ph.D., of the department of pediatrics (neonatology) at Stanford (Calif.) University, concurred, saying, "That is a question I was going to ask. ... So I know education was part of the analysis, but what socioeconomic status variables did you adjust for?"
"We did adjust for household income in all of our models. Unfortunately, this is a variable collected by the NBDPS, and it has a high rate of ‘missing,’ mothers who elected not to give household income. I think we had over 10% missing for this particular variable, but we did include that in the models."
The investigators analyzed data for 8,786 births between 1997 and 2007. All analyses excluded women with diabetes as it has been shown to be a strong risk factor for anotia and microtia, noted Ms. Hoyt.
The incidence of birth of an infant with anotia or microtia was 7.2% among U.S.-born Hispanic women and 11.0% among foreign-born Hispanic women, dramatically higher than the 2.3% among non-Hispanic white women, she reported.
In adjusted analyses stratified by sociodemographic factors, the elevated risk of having an infant with anotia/microtia associated with Hispanic versus white ethnicity was especially marked among strata of women having less than 12 years of education (odds ratios, 4.9-8.8), those having a body mass index exceeding 30 kg/m2 before conceiving (OR, 3.7-11.9), those who smoked in the periconceptional period (OR, 8.2 for foreign-born women), and those who did not take folic acid supplements periconceptionally (OR, 2.7-5.2).
In further analyses looking at acculturation factors and including infants having both a non-Hispanic white mother and father as the comparator group, the risk was elevated for Hispanic mothers who predominantly spoke English (odds ratio, 2.4), but more so for those who predominantly spoke Spanish (OR, 4.5). Similarly, the risk was elevated for U.S.-born Hispanic women (OR, 2.5), but more so for Mexican-born women who immigrated after age 5 (OR, 4.9).
Ms. Hoyt disclosed no relevant financial conflicts.