As Babies Are Born Earlier, They Risk Problems Later
Saturday, May 20, 2006
More and more babies each year are being born just shy of spending a full pregnancy in their mothers' wombs, putting more infants at risk of health and possibly developmental problems because they enter the world before they are ready.
The percentage of babies born slightly early has been increasing steadily for more than a decade and is now at an all-time high. So many babies are being born a few weeks early -- more than 350,000 annually -- that the average U.S. pregnancy has shortened from 40 weeks to 39.
The increase is driven by a combination of social and medical trends, including the older age of many mothers, the rising use of fertility treatments and the decision by more women to choose when they will deliver. At the same time, medical advances are enabling doctors to detect problem pregnancies earlier and to improve care for premature babies, prompting them to deliver more babies early when something threatens their lives or those of their mothers.
Many obstetricians argue that the trend is positive overall because they are preventing thousands of stillbirths and avoiding potentially serious risks for mothers. But other experts worry because these babies are prone to a long list of serious, potentially life-threatening complications, which often require intensive, costly treatment. Moreover, growing evidence suggests that their long-term development may be more problematic.
"We should be concerned about these babies," said Tonse N.K. Raju of the National Institute of Child Health and Human Development. "They have more short-term problems, and there is evolving evidence that they have long-term risks as well."
Although most of these babies fare well and face far less risk than very premature infants, researchers have begun to realize that they are nevertheless more prone to short-term complications, such as problems breathing and feeding, and jaundice. And because so many are being born each year, even a small increased risk translates into thousands of sick babies. Studies are also starting to suggest that these children may tend to not develop as well as full-term babies, leading to behavioral, learning and other difficulties.
"There's no question these babies tend to have more [immediate] problems compared to full-term babies," said Richard E. Behrman of the Federation of Pediatric Organizations, who chairs a panel assembled by the National Academy of Sciences that will issue recommendations on the rising late-preterm birth rate next month. "The concern is about whether there is some adverse impact on their long-term development."
For years, most of the attention focused on the earliest, smallest "preemies" -- those born before 32 weeks -- because they face the greatest risks of dying or having permanent disabilities, such as cerebral palsy, deafness and blindness. But the proportion of babies born that early has leveled off, while the rate of "near-term" or "late-preterm" births -- between 34 and 36 weeks -- continues to rise. They now account for about two-thirds of all preterm births.
"These kids have been below the radar screen," said Marie C. McCormick of the Harvard School of Public Health. "They're just starting to get our attention."
Nearly 9 percent of all babies delivered in the United States were born late-preterm in 2003, according to the most recent federal data. That is up from 7.6 percent a decade earlier and the highest since the government started tracking such births -- and translates into about 50,000 more of these babies each year.
"It's a huge increase," said Mary E. D'Alton of Columbia University. "The question is: Are we doing too many of these deliveries?"
While the precise cause of the increase is unclear, one reason is that more women are delaying childbearing until their thirties, when they are prone to complications, including premature labor. Older women are also more likely to need fertility treatments, which increase the chances of having twins and triplets -- which tend to be born early. The obesity epidemic may also play a role -- obese women have more complications, such as high blood pressure and diabetes, that can make it necessary to end a pregnancy early.