Newly-released research shows that the survival odds for preterm babies are improving.
A study by Duke investigators demonstrated that there has been a slight improvement in the survival rate of babies born 22 to 24 weeks into their gestation period. These babies—who barely weigh more than a pound—are suffering significantly fewer developmental consequences as a result of their premature birth, the study discovered.
Only 30 percent of the babies born at the beginning of the study—from 2000 to 2003—survived, but this increased to 36 percent for the babies born at the end of the study, from 2008 to 2011. However, the overall survival rate for babies born at 22 weeks remained at four percent.
“The most important thing is that there’s some improvement over time in the outcomes of these 22 to 24 week gestational age babies,” said Charles Michael Cotten, professor of pediatrics and a senior author of the study.
Babies born this early face many obstacles. Most of their organ systems are not yet fully developed—their lungs are not yet capable of exchanging oxygen and carbon dioxide, their digestive systems are not ready to absorb nutrients and the blood vessels near their brains are weak and prone to breaking.
Normally, babies would spend another three to four months in the womb developing. Once born, however, they are placed into a neonatal intensive care unit where they receive special around-the-clock treatment from doctors like Cotten and Noelle Younge, the study’s lead author and a neonatologist and assistant professor of pediatrics at the School of Medicine.
“We aren’t as good as a mom and a placenta,” Cotten said. “We’re trying to, but we have a long way to go.”
Much of this neonatal care has improved over the past 10 to 15 years, leading the doctors to believe it is a major cause of the improved outcomes. Preterm babies are prone to infection since they lack a fully-developed immune system, so doctors and nurses have taken new steps to reduce the risk that they will get sick.
“We saw that fewer of them had infection over time,” Younge said. “Infection is linked to poor long-term neurodevelopment outcomes in previous studies.”
Other improvements include preterm babies being fed their mother’s milk and mothers who are at risk for preterm birth being given steroids to speed the baby’s development process.
The study used birth data over 12 years from the National Institute of Child Health and Human Development’s Neonatal Research Institute Network. Duke’s neonatal intensive care unit participates in the research institute and serves as a large referral unit for the region. Younge said that Duke’s unit has seen good outcomes compared to others.
When the preterm babies were evaluated as two-year-olds, the proportion with cognitive and motor impairments did not change over time, but the proportion who survived without severe neurological conditions increased.
Such tests are not perfect indicators, but Younge and Cotton emphasized that they can be predictive of later life outcomes, which remain more fraught for such babies. Some studies have shown higher rates of cardiovascular disease, diabetes and other diseases after premature births. Recognizing this, more primary care doctors have begun asking patients whether they were born premature, Cotten said.
Although the improvements seen in the study may not seem large, they provide useful data for doctors as they counsel families who may be at risk of having a baby pre-term.
The causes of premature birth are not fully understood. About one in 10 babies are born premature, but only a small fraction of those are born in the extreme 22 to 24 week category.
Younge said she looks forward to future studies on these premature births, particularly about bacteria found in the babies' digestive systems, new nutritional practices and potential clinical trials. Still, Cotten said there is much room for improvement in the survival odds of preterm babies.
"There’s a large number, the majority [of babies], who don’t have a good outcome," he said. "It’s a reminder and stimulus that we have a lot of work still to do.”
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Adam Beyer is a senior public policy major and is The Chronicle's Digital Strategy Team director.