However, at present, there is no reliable way to prevent or delay preterm birth, says Christopher P. Howson, Ph.D., vice president for Global Programs of the March of Dimes. "While much can be done right now to reduce death and disability from preterm birth even in low-resource settings, we need to know more about the underlying causes of premature birth in order to develop effective prevention strategies," he says.

The March of Dimes and the other authors of the white paper call for greater efforts to inform health professionals, policy makers, women of childbearing age, and others about the worldwide toll of preterm birth and opportunities for prevention and for care of women with high-risk pregnancies and their babies.

Preterm Births: Why Don't They Count?

Few countries currently have good health statistics and information systems or birth surveillance registries, the authors of the white paper say, so data on the number of preterm births and related deaths are limited at best.

"This was a first attempt to estimate the worldwide scale of the problem," says Mario Merialdi, M.D., of WHO's Department of Reproductive Health and Research, one of the editors of the White Paper and an author of the study published in The Bulletin of WHO. "As a first step, it is necessary to improve data on the extent of the problem." He says WHO currently is improving its database on preterm birth in order to support decision-making in this area.

Another challenge, the authors of the white paper say, is that there is no internationally accepted classification of preterm birth or glossary of terms. "We need to at least adopt common definitions and agree on what is a preterm baby," says Joy E. Lawn, MRCP, of Saving Newborn Lives/Save the Children USA.

Dr. Lawn says there also is an urgent need for more country and regional data on the prevalence of acute and long-term health problems and impairment caused by preterm birth.

Almost 13 Million Preterm Births Worldwide

Preterm birth rates by national income category:

In high resource regions, 1,014,000 infants each year are born preterm, or 7.5 percent of total births. In middle resource regions, 7,685,000 infants are born preterm, or 8.8 percent of total births. In low resource regions, 4,171,000 infants are born preterm, or 12.5 percent of total births.

Source: March of Dimes Foundation