that for diseases such as diabetes or hypertension, which are influenced by multiple genetic, social, personal, and environmental factors. Although the biological reasons for differences across ethnic background have not been identified, certain populations have a substantially greater risk for prematurity, and prematurity rates vary by region across the country. For example, substantial differences between African Americans and Caucasians have been found in preterm birth rate and infant mortality associated with prematurity (Healthy People 2010). These differences are difficult to understand biologically, suggesting that environmental factors play a role. We must consider carefully what these environmental factors might be, because understanding the factors that influence these variations will help us develop a better sense of the cause of prematurity and strategies for preventing it.

Among the five leading causes of infant mortality, two—low birth weight and respiratory distress syndrome—are associated with being born too early. The economic costs of preterm birth are substantial, both at the beginning of life and throughout its course. Data from the Agency on Healthcare Research and Quality reveal that two of the five most expensive hospital conditions in the United States in 1997 were associated with prematurity (AHRQ, 1996). Respiratory distress syndrome, the most expensive condition, had a mean hospital charge of $68,000 and a length of stay of more than 24 days. Low birth weight did not lag not far behind, with a $50,000 mean hospital charge and a length of stay of more than 21 days. These data are for children who are discharged alive. We have begun experimenting with community interventions to try to understand how we can influence these outcomes.

Preterm deliveries fall into three broad categories or pathways. The first category is medically indicated early deliveries—those necessitated by maternal or fetal factors. In such cases, it is believed that whatever the potential consequences of prematurity may be, early delivery is much safer for both the mother and the child. The other two categories—early deliveries due to spontaneous preterm ruptured membranes and those due to spontaneous preterm labor—may respond to intervention. As ones knowledge of etiology improves, all of these pathways may yield to prevention. Some participants have asked that we consider the possibility that early deliveries in all three categories are modifiable. Some have suggested that the factors influencing early delivery in each of these categories may be the same. Thus, we need to examine whether the strategies for preventing early delivery in one category may prevent conditions associated with another category. One charge for this workshop is to consider why we have created separate categories, which may be artificial, and how prevention strategies may affect all categories simultaneously.

An underlying truth regarding prematurity that relates to the issue of separating individual, environment, and genetic factors is the unfortunate observation that the best predictor of having a preterm birth is having experienced one previously (Mattison et al., 2001). The risk increases with each successive preterm



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement