Preterm births at 10% globally
More than 1 million die in their first month because they were born early, study says.
WASHINGTON - Around the world, one in 10 babies is born prematurely each year, and such early birth is the reason that more than one-quarter of them die in their first month of life.
Those are among the findings of a new study of the burden of preterm birth by the World Health Organization and the March of Dimes.
The study, to be followed with a country-by-country assessment next year, looks at the specific role of prematurity in the problems of newborns.
"These are striking data that really surprised us," said Christopher Howson, a March of Dimes researcher who helped prepare the report.
According to the study, 12.9 million babies are born too soon each year, representing 9.6 percent of all births. Of 4 million deaths recorded soon after birth, 28 percent are attributable to prematurity.
Some of the information provided by WHO was only for women pregnant with one baby. Women carrying multiples have a much greater risk of delivering early.
"We know the figures in this report are conservative," Howson said. "I think we can say very clearly that the situation on the ground is more dire than this suggests."
Preterm birth is defined as birth before 37 weeks of gestation. A typical pregnancy lasts 40 weeks. Rates and causes of preterm birth vary widely by region.
Africa has the highest rate (11.9 percent), followed by North America (10.6 percent) and Asia (9.1 percent).
Latin America and the Caribbean are midrange (8.1 percent), and Australia and New Zealand (6.4 percent) and Europe (6.2 percent) are the lowest.
Relatively little is known about the causes of prematurity in the developing world. However, malnutrition, coexisting illnesses such as malaria and anemia, and inadequate prenatal care are likely factors, Howson said.
Other variables are probably at play in the United States, where the rate of preterm birth has increased 36 percent in the last quarter-century. The U.S. rate is 12.7 percent; the North American rate is brought down by Canada's 8.2 percent rate.
The increase in the number of older women having babies and reproductive techniques that make multiples more likely probably contribute to the trend. Black women also have a 50 percent higher rate of preterm delivery than white women do.
Most of the increase in preterm birth in the United States is from deliveries between 34 and 36 weeks of gestation, known as "late preterm" birth. Once thought to present little risk, even that lesser degree of prematurity is now known to be hazardous.
In a study published last year, the University of Texas Southwestern Medical Center in Dallas examined 18 years of single-birth records.
Late-preterm babies were 9 percent of all deliveries and 76 percent of all premature births. Mortality was low, but more than twice that of full-term babies. The preemies also were more likely to need breathing assistance, be jaundiced, and develop infections.
Eighty percent of the late-preterm births were the result of early labor or rupture of membranes, problems that are usually without obvious cause.
The new study did not outline strategies for reducing preterm births globally, but a more detailed study due next year is expected to.