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 "We've seen a slight increase in the number of infants who survived
without signs of impairment at 2 years of age," chief author Dr.
Noelle Younge of Duke University in Durham, North Carolina, told
Reuters Health.
For the study, published in the New England Journal of Medicine,
Younge and her colleagues looked at survival rates, with and without
disability, for these extreme preemies over three periods - from
2000 to 2003, from 2004 to 2007 and from 2008 to 2011.
A typical pregnancy lasts about 40 weeks, and babies born before 37
weeks are considered preterm. Those born much earlier, at around 22
to 24 weeks gestation, are considered to be at the limit of
viability and likely to have serious neurological and other
problems.
Understanding the likelihood of survival and the odds for
disabilities can help doctors counsel parents of extreme preemies
about their child’s prognosis, the study team writes.
Younge’s team found that among all children born at 22 to 24 weeks,
rates of survival without neurodevelopmental impairment - which was
assessed at age 18 to 22 months of corrected age - increased by 4
percentage points from the earliest study period to the most recent.
But the actual odds were small at the start and remained small, with
impairment-free survival going from 16 percent to 20 percent.
The death rate declined from 70 percent in the first period to 64
percent in the most recent period.
The real improvements were seen in children born at 23 weeks and 24
weeks. The impairment-free rates went from 7 percent to 13 percent
in the 23-week group and from 28 percent to 32 percent in the
24-week group.
The researchers said lower rates of infection and the greater use of
steroids given to mothers to help the fetus mature faster may be
responsible for the improvements.
But those interventions have their limits.
There was no comparable improvement over the 12-year study period
for babies born at 22 weeks gestation. Only 1 percent survived
without neurodevelopmental impairment.
The raw survival rates showed a similar pattern, with most of the
improvement reflecting higher survival rates among infants born in
the 24th week.
In that group, the rates went from 49 percent in the earliest period
to 56 percent in the most recent one.
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In comparison, in 2008-2011, survival rates were 24 percent if the
baby made it to 23 weeks gestation compared to just 3 percent if the
baby was born at 22 weeks.
"With the 22-weekers we didn't see a lot of difference," said Younge,
a neonatologist and assistant professor of pediatrics at Duke. "At
23 weeks we did see an improvement over time."
That seems to be the key demarcation point because "between 22 and
23 weeks, the lungs are really maturing. The brain is maturing. So
in this 22-week window certain infants have met maturation
milestones and can survive," she said.
The researchers caution that "there is likely to be substantial
variation” in the long-term functioning of children classified as
having neurodevelopmental impairment in early childhood.
"Although early neurodevelopmental assessment is important for the
timely identification of children at risk for long-term neurologic
impairment or developmental delay, its capacity to predict later
functioning is limited," the study team writes. "Many children will
catch up to their peers by school age, whereas other children will
have persistent impairment. Conversely, some children without signs
of neurodevelopmental impairment in early childhood will have
impairments that manifest at school age."
SOURCE: http://bit.ly/2lICPue New England Journal of Medicine,
online February 15, 2017.
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