Different population groups in the United States and California experience different burdens of prematurity and growth retardation. Disparities in any health outcome sometimes provide clues regarding the causes of disease. Perhaps more importantly, they enable us to understand patterns of health outcomes as social justice issues.
The ways in which we discuss these patterns are largely determined by the data sources that we have. Birth certificate records contain two types of information that help us in this regard: (a) mother's racial and ethnic identification (although this may be recorded inconsistently), and (b) the location of the mother's residence at the time of delivery.
The causes of these disparities have yet to be explained. At least part of the pattern appears to be due to the effects of poverty on nutrition, stress, and access to health services. Some researchers have suggested a role for a "preterm birth gene", and physiological differences in maternal responses to inflammation between races have been noted. Others, however, have pointed out that the genetic heterogeneity of US populations makes it unlikely that genes could be responsible for such a persistent social pattern.