Pediatrics published research that states children in Ireland and the United Kingdom born at less than 25 weeks gestation are at greater risk for pervasive behavioral problems.   Boys are at greater risk than girls. 

Reference:  Samara, Muthanna, Marlow, Neil, Wolke, Dieter, for the EPICure Study Group, Pervasive Behavior Problems at 6 Years of Age in a Total-Population Sample of Children Born at <=25 Weeks of Gestation Pediatrics 2008 122: 562-573