New York, US: A ‘lottery of birth’ is at play in many developing countries where poorer, socially disadvantaged children are more likely to die than their more fortunate peers, according to a leading children's charity.

Save the Children said that in 78 percent of the 87 low and middle income countries it analysed in its ‘Lottery of Birth’ report, at least one social or economic group was lagging behind and making slower progress in reducing child mortality.

In 16% of those countries, the gap in child mortality rates had increased across all social and economic groups.

"In this day and age, it is scandalous that so many children's chances of survival across the world is purely a matter of whether or not they were lucky enough to be born into an affluent family who can access quality healthcare," Jonathan Glennie, director of policy and research at Save the Children, said in a statement.

Living in the countryside and belonging to a marginalised ethnic group are among the factors that play a huge role in a child's chances of survival, the report said.

Disparities in child mortality rates between ethnic groups increased in 76% of the countries studied, it said.

In Indonesia, children born into the poorest 40% of households in 2012 were almost 2.5 times more likely to die than their peers in the richest 10 percent, the study found.

However, almost a fifth of the countries examined for the report had achieved rapid and inclusive reductions in child mortality, it said.

Some countries have made huge strides in ensuring the survival of children, saving tens of millions of lives since the Millennium Development Goals were set, Save the Children said.