By Salynn Boyles
Aug. 6, 2001 -- Justin Washington could literally fit in the palms of his mother's cupped hands when he was born six years ago in a Nashville hospital. Dorenda Washington was one month past the halfway point in her pregnancy when she learned there was nothing more that could be done to stop her baby from coming.
Born at 24 weeks, weighing just 1 pound, 8 ounces, Justin remained in neonatal intensive care for more than four months and had countless surgeries before finally going home with his parents. Today he is a healthy, happy little boy who likes to swim and ride his bike and who wants to be president some day, his mom says. The March of Dimes chose Justin as their 2001 national ambassador to highlight the issue of premature birth, and the Washingtons now travel all over the country to bring attention to the issue.
"We are incredibly lucky," Dorenda Washington tells WebMD. "When they give you the news that your child is going to be born halfway through your pregnancy, and you don't know if he is going to survive, all you can do is pray and rely on the people who are trained to deal with this. They become family."
Dramatic Increase in Preterm Births
Premature births are on the rise in the U.S. Since the early 1980s, the rate of early deliveries has risen by 23%, and today approximately 11% of all births -- or 450,000 each year -- occur early. A full-term pregnancy is 40 weeks, and babies are considered premature if they are born prior to 37 weeks.
For largely unknown reasons, black women have twice the rate of preterm deliveries as white women, and this remains the case across the economic spectrum.
"It is one of the biggest frustrations for those of us in the field of maternal and child health," says Donald R. Mattison, medical director for the March of Dimes. "Infant [deaths are] falling, and we know much more than ever about improving maternal and infant health, but prematurity is getting worse."
It sounds paradoxical that premature deliveries are increasing at a time when clinicians know more than ever about keeping pregnant women and their babies healthy. But experts say medical advances actually explain most of the increase in early births. The main culprit, they say, is the increase in multiple births over the past 20 years due to the growing use of assisted reproduction techniques like in vitro fertilization.
Twin birth rates rose by 52% and high-order births (triplets or more) rose by an astounding 404% between 1980 and 1997, according to figures from the National Center for Health Statistics. There were only about 1,000 high-order births in the U.S. each year prior to the introduction of assisted reproduction. Today, there are between 6,000 and 7,000.
"Assisted reproduction, as it has been practiced, carries a high risk of multiple births. With multiple births you can be absolutely certain of having more preterm deliveries," says epidemiologist David A. Savitz, PhD. "Studies have suggested that at least a third of the total increase in preterm births can be attributed to multiple gestations."
Thanks to advances in diagnostic testing, obstetricians are also better able to monitor fetal and maternal distress than they have been in the past. As a result, inducing labor between 35 and 37 weeks gestation is far more common than it once was. The practice is somewhat controversial, and some argue that is being done too often.
"The willingness of clinicians to deliver early is probably greater now than it has ever been," Savitz says. "I don't think they perceive any problem whatsoever at delivering a baby at 35 or 36 weeks. But when you look at large population studies, these babies do have a slightly increased risk of [death] and certain developmental problems."
Charles J. Lockwood, MD, who leads the American College of Obstetricians and Gynecologists' committee on obstetrical practice, has a different view. Induction prior to 37 weeks is virtually never done without good reason, he says.
"Early inductions have certainly increased, but the reasons behind them more than justify the reasons for doing them," Lockwood tells WebMD. "Fetuses in distress are more likely to die and have long-term problems, so there are very good reasons for delivering them between 35 and 37 weeks."
Early Delivery: 'A Problem We Should Have Solved'
While the rise in preterm deliveries may be explainable, doctors have had less success preventing naturally occurring early births. It is widely believed that stress and infections play a major role -- accounting for roughly 70% of premature deliveries, Lockwood says -- but ob-gyns have not yet figured out how to treat these labor triggers. Trials using antibiotics to treat infections in pregnant women have so far been disappointing.
"With all of our new toys and equipment, and with all of our new leaps in gene research, we still don't know how to keep women from delivering early," says epidemiologist Claudia Holzman, PhD, of Michigan State University. "The big story isn't that preterm deliveries are on the increase, it is that we haven't solved the problems that cause them."
"The fact is, this is a problem we should have solved, but we are still grappling with it," echoes the March of Dimes' Mattison.
Holzman and MSU colleagues are evaluating sources of stress and responses to it in a group of 1,500 women being followed from midpregnancy. The researchers are studying stress-related responses such as blood pressure, heart rate, and hormone levels.
Hormones released in response to stress may make blood vessels narrow, causing damage to the placenta and prompting premature delivery. Stress responses may also damage the immune system, promoting uterine infections implicated in premature delivery. And stress is believed to boost production of a hormone -- called corticotropin-releasing hormone -- that is thought to play a role in triggering labor.
"Some studies suggest that if a woman is abused or neglected early in life, she may be hypersensitive to stress," Holzman says. "She may put out more stress hormones, which can affect pregnancy."
Savitz, who is chairman of the department of epidemiology at the University of North Carolina, Chapel Hill, is principal investigator for the ongoing Pregnancy, Infection, and Nutrition study, one of the largest and most comprehensive studies to date exploring the potential causes of preterm delivery. Researchers are currently looking at data gathered from 3,000 women and hope to enroll another 2,000 in the study, which examines social, economic, nutritional, and biologic factors possibly related to premature births.
So far, Savitz says, the researchers have found no previously unidentified factors responsible for premature delivery. In fact, analysis of preliminary data suggest that several behaviors thought to be associated with preterm delivery -- like smoking cigarettes and using cocaine -- may not be.
"Obviously, both of these things play a big role in fetal development, but our findings suggest they don't influence delivery," Savitz says. "There are a lot of hypotheses and very little clear data on what the relevant risk factors for preterm birth are. I wish I could tell you we have some striking new evidence of what causes this, but so far we are finding more things that aren't related."
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