Aug. 15, 2000 -- Women who give birth prematurely are often concerned about the long-term effects on their babies. While extremely premature babies receive a great deal of attention, there has been less information about babies born two to six weeks premature. Now new research sheds light on the effects of being born at 32 to 36 weeks.
A term pregnancy lasts anywhere from 38 to 42 weeks after a woman's last menstrual period, and a baby born between 20 and 37 completed weeks of pregnancy is considered premature. Preterm birth is the leading cause of death in infants born in developed countries. Now, researchers have found that even babies born just a few weeks too early can be at increased risk of death from a variety of causes in the first year following birth.
The findings are important because recently some obstetricians and pediatricians have considered these births as relatively low risk for problems, and many may not have taken follow-up precautions to prevent complications. The findings were published in the August issue of the Journal of the American Medical Association (JAMA).
"Mild and moderate preterm births carry a significant risk of infant death from a variety of causes and account for a sizeable proportion of all infant deaths," study author Michael S. Kramer, MD, tells WebMD. Kramer is a professor of pediatrics and epidemiology and biostatistics at McGill University in Montreal.
To reach their conclusions, researchers from the U.S. and Canada examined millions of infant deaths, some dating back to 1985. As expected, the researchers found that the highest risk of infant death was for those babies born at less than 28 weeks. But although risk decreased as births approached full-term, infants born at 32 through 36 weeks were also at increased risk of death.
For the Canadian preemies born between 32 and 33 weeks, the risk of death increased by 15 times over that of full-term births, and death by infection was increased by 25 times over normal. Kramer and his team found the increased risk of death due to infection was highest in the first few weeks, but the risk still remained throughout the first year of life.
The babies born between 34 and 36 weeks fared better, but the risk of death during the newborn period or first year of life was still four-and-a-half times higher.
Along with deaths from infection, deaths from asphyxia, sudden infant death syndrome, and abuse were also higher. As with infection, Kramer and his team found that the first month of life was most critical.
Sadly, their findings also showed that little has changed in the patterns of death in either Canada or the United States since 1985, except for a decreased risk of death associated with infection. Kramer writes that "preventing the occurrence of mild and moderate preterm births and of death among such births remain worthy targets for future research and clinical intervention."
"It's obvious from this latest data that preterm birth is still a problem," Robert C. Cefalo, MD, PhD, tells WebMD. As a result of these findings, he says, women contemplating pregnancy or at risk for preterm birth should work with their clinicians to "avoid preterm labor and delivery" whenever possible. Cefalo is clinical professor in the department of obstetrics and gynecology at the University of North Carolina School of Medicine at Chapel Hill in North Carolina. He is also a pioneer in maternal-fetal medicine, the subspecialty dealing with pregnancy complications.
But is this a cause for alarm about any baby born early? Charles R. Rosenfeld, MD, director of neonatal-perinatal medicine at the University of Texas Southwestern Medical Center in Dallas, helps put the numbers in perspective.
"Our institution has the largest delivery rate in North America, with close to 16,000 babies a year," he tells WebMD. "Of that group, about 100 babies a year are less than 30 weeks gestation." About 500 to 600 of those babies are born between 32 and 36 weeks, he says, and "at 36 weeks gestation, we don't even put them in our neonatal care unit -- their survival rate is 95%." Rosenfeld is also professor of pediatrics and obstetrics-gynecology.
However, Mark A. Klebanoff, MD, MPH, director of the division of epidemiology statistics and prevention research at the National Institute of Child Health and Human Development in Maryland, tells WebMD: "These babies are not the same as full-term babies, and they still account for more than their share of infant mortality." Still, when it comes to the question of inducing labor, he says, "If a woman is having a complication, it becomes a question of weighing the risks of continuing the pregnancy vs. having the baby now."
Rosenfeld agrees, and adds, "This report is a reminder that we need to watch out for the big preemies as well as the little preemies."