New York, Nov 3 (IANS): Poor foetal growth -- preterm birth and low birth weight -- is the leading cause behind stunting among 25 per cent children in the developing countries, the researchers said.

In 2011, nearly 44 million (36 per cent) of two-year-olds in 137 developing countries were stunted -- defined as being two or more standard deviations shorter than the global median.

About one quarter (10.8 million) of those stunting cases were attributed to full-term babies being born abnormally small, reported the study by researchers at Harvard Chan School in the US.

In the study, the researchers identified 18 risk factors which were grouped into five categories: poor foetal growth and preterm birth; environmental factors, including water, sanitation and indoor biomass fuel use; maternal nutrition and infection; child nutrition and infection and teenage motherhood and short birth intervals (less than two years between child births).

Reducing the burden of stunting requires continuing efforts to diagnose and treat maternal and child infections, especially diarrhoea, and "a paradigm shift...from interventions focusing solely on children and infants to those that reach mothers and families," the researchers observed.

The absence of optimal sanitation facilities that ensure the hygienic separation of human waste from human contact has the second largest impact overall, attributed to 7.2 million stunting cases (16.4 per cent), followed in third place by childhood diarrhoea, to which 5.8 million cases (13.2 per cent) are attributed.

While child nutrition and infection risk factors accounted for six million (13.5 per cent) of stunting cases overall, teenage motherhood and short birth intervals (less than two years between consecutive births) had the fewest attributed stunting cases of the risk factors that were analysed -- 860,000 (1.9 per cent) of cases overall.

"These results emphasise the importance of early interventions before and during pregnancy, especially efforts to address malnutrition. Such efforts, coupled with improving sanitation and reducing diarrhoea, would prevent a substantial proportion of childhood stunting in developing countries," said lead author Goodarz Danaei, Assistant Professor at Harvard Chan School.

"This is a serious problem at every level, from individual to national. Early life growth faltering is strongly linked to lost educational attainment and the immense cost of unrealised human potential in the developing world. Stunting undermines economic productivity, in turn limiting the development of low-income countries," Danaei said.

The study was published in the journal PLOS Medicine.