Rates of Prematurity, Low Birth Weight Highest Ever

Times Staff Writer

One in eight American children born in 2004 was premature, and one in 12 had a low birth weight -- the highest rates ever recorded -- and their medical care is costing the nation $26 billion a year, according to two reports released Thursday.

The high prematurity rate “has resisted all our best efforts so far to improve it,” said Dr. Duane Alexander, director of the National Institute of Child Health and Human Development. “We don’t know why this is happening.”

Babies born before 37 full weeks of pregnancy are considered premature, and a birth weight less than 5 1/2 pounds is considered low. (A full term is 38 to 42 weeks.) The two conditions, often linked, typically require hospitalization of the infant and can lead to lifelong problems, including learning disabilities, neurological problems, lung diseases and cerebral palsy.

In 2004, 12.5% of U.S. births were premature, a 30% increase over the rate in 1981, according to a report from the National Academy of Sciences’ Institute of Medicine.


There are sharp disparities by race: 11.5% of births to white mothers were premature, compared with 17.8% to African American mothers.

Similarly, 8.1% of babies were low-birth-weight, including 7.2% of white mothers’ babies and 13.7% of black mothers’. That disparity has persisted for a long time and “is not improving,” Alexander said.

Assisted reproduction accounts for some of the increase, partly because physicians often implant several embryos to increase the likelihood of conception. About 62% of twins and 97% of triplets and higher-order multiples are born prematurely.

Another factor is advancing maternal age, said Jennifer L. Howse, president of the March of Dimes. Because of the increased number of working women and delayed marriages over the last couple of decades, more women are having children in their 30s, and that delay increases the risk of prematurity.


Medical technology is helping many of those babies survive. The U.S. mortality rate for infants has stabilized since 1999 at about 6.8 deaths per 1,000 births -- its lowest rate ever -- according to the second report, by the Federal Interagency Forum on Child and Family Statistics.

That rate also shows a strong racial bias: 5.7 deaths per 1,000 births to white mothers and 13.6 deaths per 1,000 births to black mothers.

The report also found that teenagers, who accounted for half of the single mothers who gave birth in 1970, last year accounted for only a quarter.

The forum’s report, on children in the U.S., shows that the exposure of adolescents to secondhand tobacco smoke has also declined. In the late 1980s, nine out of 10 adolescents tested had chemicals in their blood indicating exposure to secondhand smoke, which has a variety of harmful consequences.


By the early part of this decade, that figure had dropped to six in 10, “a very impressive sign of progress,” said Edward J. Sondik, director of the National Center for Health Statistics.

The proportion of high school seniors smoking every day fell from 26% in 1997 to 21% in 2004.

One piece of troubling news, Sondik said, is the rise of obesity in adolescents: 18% are overweight, a proportion that has tripled in the last 2 1/2 decades.