Although their outcomes are better than outcomes of preterm infants with gestational ages of less than 32 or 33 weeks, late preterm infants remain vulnerable to the complications of prematurity. They are more likely than fullterm infants to experience cold stress, hypoglycemia, respiratory distress syndrome, jaundice, and sepsis, yet there are wide variations among hospitals in treatments and resource use for late preterm infants (Amiel-Tison et al., 2002; Laptook and Jackson, 2006; Lewis et al., 1996; McCormick et al., 2006; Wang ML et al., 2004). Despite a relative lack of information regarding long-term outcomes, retrospective studies of children with cerebral palsy report that 16 percent to 20 percent were born between 32 and 36 weeks gestation (Hagberg et al., 1996; MacGillivray and Campbell, 1995).
Accurate estimates of gestational age and better measures of fetal and infant maturity would provide important information for clinical decision making. Recognizing the higher mortality and morbidity rates for late preterm infants than fullterm infants, health care providers and families need to weigh carefully the advantages of earlier delivery against the health, financial, and economic costs of preterm delivery.
Although the complex interplay between the duration of pregnancy, fetal and infant size and maturity, and how they are measured are sources of some confusion, evaluation of the interrelationships among these factors provides an opportunity to gain some insight into the factors contributing to preterm birth. For example, racial disparities in all aspects of health have long been recognized, and the causes of these disparities are poorly understood. Public health databases with data on births, health problems, and deaths for large populations are available for exploration; but it must be recognized that the definitions of these variables may have changed over time.
Although controversy exists over inclusion criteria for racial and ethnic subgroups, racial and ethnic disparities in preterm birth rates, birth weight distributions for gestational age, neonatal and infant mortality rates, and gestational age- and birth weight-specific neonatal mortality rates have been consistently reported (see Appendix B). In the United States in 2003, preterm birth rates were 10.5 for Asian and Pacific Islanders, 11.3 percent for whites, and 17.8 percent for African Americans (Chapter 1). In 1997, the birth rates for white, Hispanic, and African American infants with gestational ages less than 28 weeks were 0.35, 0.45, and 1.39 percent, respectively