Extremely preterm babies — those born between 22 to 24 weeks gestation — continue to face unfavorable odds, as only about one in three survive. But a new study led by Duke Health shows that these rates are slowly improving. The findings show that, compared to extremely preterm babies born a decade earlier, a larger percentage are developing into toddlers without signs of moderate or severe cognitive and motor delay.
Improvements in survival and neurodevelopment may be the result of a number of factors, including decreasing rates of infection in the infants, along with the increased use of steroids in expectant mothers that can help mature and strengthen the fetus’s lungs prior to birth, according to the authors.
“The findings are encouraging,” said lead author Noelle Younge, M.D., a neonatologist and assistant professor of pediatrics at Duke. “We see evidence of improvement over time. But we do need to keep an eye on the overall numbers, as a large percentage of infants born at this stage still do not survive. Those who survive without significant impairment at about age two are still at risk for numerous other challenges to their overall health.”
For the study, the researchers looked at data of 4,274 infants born between the 22nd and 24th week of pregnancy, far earlier than the 37 to 40 weeks of a full-term pregnancy. The babies were hospitalized at 11 academic medical centers in the Neonatal Research Network, part of the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the National Institutes of Health.
About 30 percent of the infants born at the beginning of the study (between 2000 and 2003) survived. That number increased to 36 percent for babies born toward the end of the study (from 2008 to 2011), with the best outcomes for children born at 23 and 24 weeks. Overall survival for babies born at 22 weeks remained the same throughout the study, at just 4 percent.
Over the 12-year study period, the number of infants who survived but were found to have cognitive and motor impairment at 18 to 22 months stayed about the same (about 14 to 16 percent). However, the percentage of infants who survived without evidence of moderate or severe neurological impairment improved from 16 percent to 20 percent.
“Researchers in the Neonatal Research Network reported in 2015 that survival was increasing in this vulnerable population. One concern was that the improved survival might have been accompanied by a greater number of infants who went on to have impairments in the long term, such as cerebral palsy, developmental delay, hearing and vision loss,” said Younge.
“However, we actually are seeing a slight improvement. Because children continue to develop over years, it’s important to continue to track this data so families and providers can make the best decisions in caring for these infants.”
These improvements may be due to a number of factors, including lower rates of infection in the infants and increased use of steroids in expectant mothers. Steroids can help mature and strengthen the fetus’s lungs prior to birth. At the beginning of the study, 58 percent of the expectant mothers had received steroids to boost fetal development. That figure increased to 64 percent by the end of the study.
“The culture of neonatal intensive care units has really changed in the past decade,” said senior author C. Michael Cotten, M.D., a neonatologist and professor of pediatrics at Duke. “We’ve taken a big focus on preventing infections, and there’s a lot more encouragement and support for the use of mother’s milk than there was 15 years ago, which has also been linked to better outcomes.”
Extremely preterm infants are highly susceptible to infections. Neonatal intensive care units have reported steady decreases in infection rates among extremely preterm infants over the past two decades.
“This is important because infections have been associated with greater risk of neurologic problems,” Cotten said.
The study is published in the New England Journal of Medicine.
Source: Duke Health