Unicef warned Monday of what it described as grim trend lines for the world’s poorest children over the next 15 years, saying in a new report that many millions face preventable deaths, diseases, stunted growth and illiteracy.

The forecasts in the report by Unicef, the United Nations Children’s Fund, suggested that despite reductions of poverty and other deprivations in underdeveloped countries since 2000, as seen in improved national averages, those statistics had obscured a worsening trend among the poorest segments of their populations and may have impeded overall progress.