About 13 million babies are born too soon each year worldwide, and one million of them die, according to a report released Sunday.

The March of Dimes, an international group that aims to improve the health of babies, looked at premature births and the consequences, based on data from the World Health Organization (WHO).

The group found more than 10 per cent of births in North America, or 500,000 babies, are preterm, up 36 per cent since the mid 1980s. Africa had the most preterm births — 12 per cent.

The causes are very different between the two regions, said Christopher Howson, vice-president for global programs at the March of Dimes Foundation in Washington.

Poor conditions and lack of health care are to blame in Africa. In North America, the benefits of medical advances and better general health have been offset by the rising number of women over age 35 having babies, and the increasing use of assisted reproductive technologies that result in multiple embryos being implanted.

"Studies show that moms who are carrying twins or higher order multiples are at six times the risk of having a preterm baby as a mom who's carrying a single baby," said Howson.

If they survive, preterm babies are more likely to have problems including:

  • Developmental or behavioural issues.
  • Learning disabilities.
  • Cerebral palsy.
  • Respiratory illness.

The largest proportion of the increasing preterm birth rate in North America is a result of late preterm births — babies born after 34 weeks of gestation. The WHO defines normal term delivery as between 37 weeks and 42 weeks.

Until recently, it was thought the late preterm babies weren't a cause for a concern, but that has changed.

It's now recognized that late preterm babies face higher rates of re-hospitalization, jaundice and delayed brain development, Howson said. "So there is a risk with being born even a week or two weeks too soon."

The 13-page report from March of Dimes is intended to bring more attention to the dangers of preterm birth. It calls for more international co-operation, public health measures to improve the health of babies and mothers, and more funding to make those things happen.

The group plans to follow with another report next year suggesting more specific strategies to reduce the deaths and disabilities associated with preterm births.