The reasons for low birthweight are very different in poor and rich regions.

More than 20 million newborns in 2015 -- one in seven -- came into the world weighing too little, according to a global assessment of birthweight, published Thursday.

Over 90 percent of babies tipping the scale at less than 2.5 kilos (5.5 pounds) when born were in low- and middle-income countries, researchers reported in The Lancet Global Health.

Worldwide, just under 15 percent of 2015 newborns in the 148 countries canvassed had low birthweight, varying between 2.4 percent in Sweden and nearly 28 percent in Bangladesh.
That's down from a global average of 17.5 percent in 2000.

But meeting the World Health Organization target of cutting low birthweight 30 percent between 2012 and 2025 "will require more than doubling the pace of progress," said lead author Hannah Blencowe, a professor at the London School of Hygiene & Tropical Medicine.

Underweight newborns who survive also have a greater risk of stunting as well as developmental and health problems, including diabetes and cardiovascular disease.

"National governments are doing too little to reduce low birthweight," Blencowe said in a statement.

Undernourished mothers

"To meet the global nutrition target of a 30 percent reduction by 2025 will require more than doubling the pace of progress."

The reasons for low birthweight are very different in poor and rich regions.

In South Asia and parts of sub-Saharan Africa, a large percentage of underweight babies are born at term but are stunted because their mothers were undernourished.

In North America and Europe, a higher share of low birthweight babies are preemies.
Adolescent pregnancies, a high prevalence of infection, high levels of fertility treatment, and a high rate of caesarean sections -- especially in the United States and Brazil -- can all be factors, the study found.

An international team of researchers analysed national government databases to estimate the prevalence of low birthweight in 148 nations from 2000 to 2015.

Overall, the study took into account 281 million births. Several countries -- including India -- were not included for lack of data.

Agence France-Presse