Preterm Birth has increased over the last decades in developed countries; the mayor contribution to this increase has been from "late preterm" births (LP). Recent publications show higher rates of mortality and morbidity for LP compared with full term infants, both in the short and long term; the risk of mortality and morbidity increases with decreasing gestational age, the lowest risk being at 39 weeks of gestation. Complications of LP birth are related to immaturity of the different organs and systems. During the neonatal period, the most frequent complications are Hyaline Membrane Disease, Transient Tachipnea, Hypoglycemia, Hyperbilirubinemia and feeding problems. In the long term, outcomes show that LP have an increased risk for developmental delay, academic and behavioral difficulties. While most complications are less frequent and less severe than extremely preterm infants, the large number of children that are born as LP represent a large population at risk. The purpose of this article is to review available evidence on mortality, morbidity and long term development in LP. This data may help obstetricians, neonatologists, pediatricians and public health workers to pay attention to this new population at risk.