The Prematurity Puzzle
Interl, Jeneen, I, Newsweek
Byline: Jeneen Interlandi
Research on early births could hold clues to disorders like autism and cerebral palsy.
Every year approximately 12.9 million babies--roughly 10 percent of all newborns around the world--are born too early, which is to say, before 37 weeks in utero. Despite a heroic, costly, and decades-long effort by doctors and scientists to understand and prevent preterm birth, that number has climbed steadily for the past three decades. In the U.S. alone, premature births are up 40 percent since 1980. Meanwhile, as modern medicine helps more and more of those babies survive, doctors and scientists have found themselves confronted with a new dilemma: how to prevent the string of neurological problems and developmental disabilities that plague many premature babies as they grow into children and adults.
Some of the factors behind the rise in preterm births are obvious: more women having children later in life (the risk of delivering prematurely increases as women get older), more families using in vitro fertilization (with its tendency toward multiple births), and more doctors opting for Caesarean sections at the first signs of fetal distress. But even among women who do none of these things, preterm births are still increasingly common. The fluid-filled membrane that surrounds the uterus ruptures decidedly ahead of schedule, sending mother into labor before baby is fully developed. Doctors still have no idea why this happens or how to prevent it. "Preterm birth is a huge, thriving area of research," says Amy McKenney, a perinatal pathologist at Stanford University Medical Center. "But for all of it, we haven't made much of a dent."
A $75 million educational campaign by the March of Dimes has managed to reduce incidence by a smidgen, from 12.8 percent in 2006 to 12.3 percent in 2008, mostly by persuading more pregnant women to quit smoking and more doctors to avoid elective C-sections in all but the direst cases.
But other efforts have failed spectacularly. "The most common interventions recommended to prevent or treat preterm labor have proved to be of little or no benefit," says Louis Muglia, a neonatologist at Vanderbilt University. For example, doctors learned in 2000 that certain bacterial infections increase a mother's chances of delivering early. But treating those infections with antibiotics does not reduce the risk of preterm delivery or improve the baby's prognosis. Likewise, women whose cervixes have shortened to less than 25mm in length by their second trimester are three times as likely to deliver early, according to studies done in 2001. But placing a cerclage, or stitch, in the cervix to help prevent further shortening has proved to be of almost no value. And while several clues point to a genetic component--preterm births tend to run in families and are higher in certain ethnic populations--the hunt for offending genes has been inconclusive at best.
Where we have improved is in keeping preemies alive. As recently as 1940, babies who were born too early or too small were often listed as stillborn and left for dead. Today we devote entire hospital wings--not to mention $26 billion in annual health-care costs--to keeping the frailest of newborns alive. Like giant mechanical wombs, neonatal intensive-care units employ a vast array of machinery to protect preterm babies from the outside world: incubators isolate them from pathogens while a host of machines and medications regulates body temperature and keeps tiny lungs working until baby is strong enough to do those things on her own. The result: 80 to 98 percent of preemies born in the U.S. now survive.
But so far, not even the best hospital in the world can fully substitute for a mother's womb. Preemies who survive the neonatal intensive-care unit frequently go on to experience a range of developmental disabilities as they grow. Some suffer from behavioral problems like attention-deficit/hyperactivity disorder, others develop more serious conditions, including mental retardation, cerebral palsy, and, according to two recent studies, autism. …