Race, genes and preterm delivery.

High rates of preterm delivery (PTD) among African Americans are the leading cause of excess infant mortality among African Americans. Failure to fully explain racial disparity in PTD has led to speculation that genetic factors might contribute to this disparity. Current evidence suggests that genetic factors contribute to PTD, but this does not imply that genetic factors contribute to racial disparity in PTD. Environmental factors clearly contribute to PTD. Many of these factors acting over a women's life prior to pregnancy disproportionately affect African Americans and contribute significantly to racial disparity in PTD. Thus, inferring genetic contribution to racial disparity in PTD by attempting to control for environmental factors measured at a single point in time is flawed. There is emerging evidence of gene-environment interactions for PTD, some of which disproportionately affect African Americans. There is also evidence of racial differences in the prevalence of polymorphisms potentially related to PTD. However, to date there is no direct evidence that these differences contribute significantly to racial disparity in PTD. Given the complexity of polygenic conditions such as PTD, the possibility of any single gene contributing substantially to racial disparity in PTD seems remote.