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close this bookCauses and Consequences of Intrauterine Growth Retardation, Proceedings of an IDECG workshop, November 1996, Baton Rouge, USA, Supplement of the European Journal of Clinical Nutrition (International Dietary Energy Consultative Group - IDECG, 1996, 100 pages)
close this folderSocioeconomic determinants of intrauterine growth retardation
View the document(introductory text...)
View the documentIntroduction
View the documentSocioeconomic disparities in IUGR: Mediating factors
View the documentSecular trends in IUGR and its determinants
View the documentAre there residual socioeconomic disparities in IUGR?
View the documentReferences
View the documentDiscussion

Introduction

One of the most robust findings in epidemiologic research on the etiology of low birth weight (LBW) has been the large socioeconomic disparities in both intrauterine growth retardation (IUGR) and preterm birth (Kramer, 1987; Parker et al, 1994; Wilcox MA et al, 1995; Kogan, 1995). In a now classic paper, Villar and Belizan reported data from 11 different regions in developed countries and 25 in developing countries (Villar and Belizan, 1982). Their analysis indicated that in developing countries, most low birth weight is due to IUGR, whereas in developed countries (especially those with the lowest LBW rates), most is due to preterm birth (Villar and Belizan, 1982). Most of the differences in LBW rates between developed and developing countries appear attributable to an increased prevalence of IUGR, rather than preterm birth, with relative risks of 6.6 and 2.0, respectively (Villar and Belizan, 1982).

Even within developed countries, however, socioeconomic disparities in birth weight have been consistently reported. These disparities occur not only in countries like the United States (Parker et al, 1994), with vast differences between the rich and the poor, but even in more 'socialistic' countries like Canada (Wilkins et al, 1991), Sweden (Ericson et al, 1993), and Denmark (Olsen and Frische, 1993) with less extreme contrasts of wealth and poverty and with universal access to high-quality prenatal and other medical care. In multiracial countries, IUGR rates have been shown to differ considerably by race, with increased IUGR rates among blacks in the U.S. (Horon et al, 1983; Showstack et al, 1984; Linn et al, 1983), aboriginals in Australia (Seward and Stanley, 1981; Sayers and Powers, 1993), and Asians in the U.K. (Dawson and Golder, 1982; Moore et al, 1995). Although a small portion of the difference may be due to true biological differences between the racial groups (Wen et al, 1995), much of it is probably linked to socioeconomic disadvantage among these racial groups. Interestingly, some other minority groups do not have the same apparent problem with IUGR. These include American Indian groups in Canada (Munroe et al, 1984; Thomson, 1990), North African immigrants in Israel (Yudkin et al, 1983), and Mexican immigrants in the U.S. (Guendelman and English, 1995); despite their socioeconomic disadvantage relative to the predominant racial/ethnic groups, these groups show birth weight distributions shifted somewhat to the right relative to the distributions dominant in their respective countries, with correspondingly low rates of IUGR.