WASHINGTON – The number of low birth weight infants who survive infancy may be reaching a plateau after 30 years on the rise,according to a recent study published in the American Journal of Obstetrics and Gynecology.
“Given the limitations of the present technology and treatments,this is about as well as we can do,” said Dr. Avroy Fanaroff,one of the study's authors and chair of pediatrics and chief medical officer at Rainbow Babies and Children's Hospital in Cleveland.
In the 1980s,about 40 percent of babies weighing between 1.5 pounds and 2.25 pounds died,Fanaroff said. By the 1990s,the mortality rate had dropped to about 13 percent.
Advances in medicine and technology – such as breathing machines,better nutrition,and antenatal steroids to help babies grow – led to greater survival rates,Fanaroff said. But now,the numbers are leveling out.
“We need another magic bullet or series of magic bullets,” Fanaroff said. “In order to go the next step,we need either to reduce the number of premature babies that are born or to come up with another spectacular treatment,and,quite honestly,there's nothing like that on the horizon. Most of what we have will give us small increments in improvement.”
Low birth weight babies are at increased risk of serious health problems as newborns,lasting disabilities and death,according to the March of Dimes,which raises money to improve children's health.
Babies born weighing less than 5 pounds,8 ounces are considered low birth weight. About 8.1 percent of babies born in 2004,the latest year for which numbers are available,met that criteria.
Doctors distinguish between premature babies and those who are small for their gestational age,though they share many of the same risks. Premature infants' risks are generally development-related,while small-for-date infants face complications because of their size.
Preterm,or premature,birth is the most frequent cause of infant death in the United States,according to a study published by the American Academy of Pediatrics in October. The study found that preterm birth causes at least one-third of infant deaths.
The infant mortality rate had dropped steadily since at least 1983,according to the National Center for Health Statistics and the Centers for Disease Control and Prevention.
In 1993,10.9 of every 1,000 infants died before their first birthdays. By 2003,the most recent year for which numbers are available,the rate was 6.8. In the last couple of years,the infant mortality rate has picked up slightly,said Robert Bock,a spokesman for the National Institute of Child Health and Human Development.
Because more babies are still being saved than 30 years ago,there is a greater rate of handicap,Fanaroff said.
Premature babies are at immediate risk of breathing problems,infection,malnutrition and the inability to control their own temperatures,said Dr. F. Sessions Cole,director of newborn medicine at St. Louis Children's Hospital. Long-term risks include smaller lung capacity and a greater likelihood of cerebral palsy and problems with eyesight and hearing.
Low birth weight children are also more likely to be obese later in life,said Frederick vom Saal,a researcher and biology professor at the University of Missouri-Columbia. Vom Saal recently released a study on some causes of obesity.
“The babies are born with a low body weight and a metabolic system that's been programmed for starvation,” vom Saal said. “The problem comes when the baby isn't born into a world of starvation,but into a world of fast food restaurants and fatty foods.”
He said low birth weight babies' bodies,designed to make maximum use of food,often overcompensate,resulting in lifelong obesity. The problem can be exacerbated with exposure to chemicals found in everyday plastics and pesticides,the study found. The chemicals alter the way genes function and make the fetus more prone to obesity and disease.
Research about preventing and mitigating the effects of low birth weight is underway.
Fanaroff noted that the prevalence of low birth weight is much greater among specific racial groups.
“Prematurity is a socioeconomic disorder as well,” Fanaroff said. “We need to decrease the racial disparity in the number of prematurities. They're much more common in African-Americans than in Caucasians,and they're much more common in the inner city than in the suburbs.”
About half of premature births are caused by an infection in the mother,placental bleeding or the presence of multiple fetuses,Cole said.
“About half of the babies who are born prematurely,we don't know what the cause is,” Cole said.
Parents can take some simple steps to help reduce the risks,Cole said.
He recommended that would-be parents talk to their doctors before they conceive to make sure they are healthy. The woman should take prenatal vitamins beginning two-to-three months before conception.
The father's sperm can also be affected by organic solvents – environmental toxins found in pesticides and other common chemicals,Cole said. Men can minimize the risk of prematurity by being as careful about exposure to these chemicals as they can,he said.
Both parents should avoid smoking,drinking and prolonged time in hot tubs,which can damage sperm in a man and the fetus in a woman.
Also,parents considering fertility drugs and their doctors should assess risks associated with having twins or triplets,who are more likely to be premature.
“The survival rate is up. We're able to save these babies,and it's terrific,” Cole said. “It also has sort of a dark side. There is a long-term health burden that these premature babies will face.”