Task 1, given the magnitude and complexity of the task, the committee determined that it was unable to address maternal weight history before entering pregnancy other than to take prepregnant BMI into account. Whenever possible, the committee sought and presented data on outcomes associated with GWG by racial/ethnic groups. This was done in the spirit of documenting disparities across racial/ethnic groups that the committee anticipated would reflect the strong socioeconomic differentials and not biological differences across these groups. This assumption is grounded in the fact that ethnicity is, by definition, a sociocultural construct and that race, as it is defined in the United States, has been shown to be a social and not a biological construct (Goodman, 2000).

It is noteworthy that the committee was not charged with evaluating either the safety or effectiveness of the IOM (1990) guidelines. However, observational studies clearly indicate that gaining within the 1990 guidelines is associated with better pregnancy outcomes (and, presumably, greater safety) than gaining outside of them (Taffel et al., 1993; Abrams et al., 2000; Gross, 2006). Moreover, the safety and effectiveness of a set of guidelines is a function of many factors, including adoption and use of the guidelines by the health care team, acceptance and actual use of the guidelines by their target audience, barriers the target audience might experience in achieving the guidelines and, finally, whether those who actually meet the guidelines have better outcomes.

CONCEPTUAL FRAMEWORK

To inform its review of the literature and to guide the organization of this report, the committee reevaluated the conceptual framework utilized in the IOM (1990) report (see Figure 1-1) to account for advances in scientific understanding of the determinants and consequences of GWG. However, it retained the same general scientific approach and epidemiologic conventions used previously and discussed in detail in the IOM (1990) report. Several changes in the conceptual framework are noteworthy. The committee chose to highlight the importance of numerous environmental factors as determinants that lead to GWG. It is recognized that some of these act through maternal factors to influence GWG and its consequences, while others may affect those consequences by other routes.

ORGANIZATION OF THE REPORT

This report is organized into eight chapters in which the committee describes what is known about GWG, with particular attention to demographic and other factors associated with weight gains that fall above or



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