The major burden of preterm birth is in the developing world, where much of the death and morbidity is secondary to infectious diseases such as malaria, HIV, tuberculosis and intestinal parasites. There is some evidence to support the concept that normal gestational length varies with ethnic group; babies of black African ancestry tend to be born earlier, more commonly pass meconium in labor, but have less respiratory distress than white European babies of matched gestational age. However, ethnic differences are tiny compared with the effects of infectious disease and malnutrition. Interventions to prevent preterm birth should predominantly be aimed at the prevention and treatment of infectious disease, and the improvement of maternal nutrition. Without this, medical intervention tends to increase the rate of preterm birth without corresponding improvement in outcomes.