More than 200 million children under the age of five in developing countries are failing to reach their development potential, a report says.
Early child development needs to be improved if the UN Millennium Goals of wiping out poverty and ensuring universal primary education are to be achieved, the report says.
Researchers link poverty and stunted growth caused by malnutrition to poor cognitive and educational performance.
Lead author Professor Sally Grantham-McGregor, of the Centre for International Child Health, University College London, says: "These disadvantaged children are likely to do poorly in school and subsequently have low incomes, high fertility, and provide poor care for their children, thus contributing to the intergenerational transmission of poverty."
The report, published in the Lancet medical journal, says that children in developing countries are at risk from poverty, poor nutrition, poor health, and unstimulating home environments, which affect cognitive, motor, and social-emotional development.
In the first of a three-part series on child development, the authors say that policymakers were failing to fully recognise the effect of poverty and malnutrition on child development, and the value of early intervention.
"The first UN Millennium Goal is to eradicate extreme poverty and hunger, and the second is to ensure that all children complete primary schooling," they write. "Improving early child development is clearly an important step to reaching these goals."
The report shows that there are 559 million children under the age of five living in developing countries. The authors say their estimate of 219 million disadvantaged children is "conservative".
They identify fewer years of schooling and less learning in school as the two pathways to reduced productivity, calculating the average loss of income when disadvantaged children reached adulthood as 19.8%.
The series of papers will go on to identify the main causes of poor child development and the methods to tackle it.
