**After talking with Helen, I have decided to make a separate post out of this study, which Helen cited in the comments of the previous post, as to make sure it doesn't get lost in another topic.**
Helen Harrison writes:
I have just seen a study In "Pediatrics" from the NICHD entitled "Unimpaired Outcomes for Extremely Low Birth Weight Infants at 18 to 22 Months" which contains some rather shocking (to me, at least) information, indicating that current outcomes are even worse than I thought.
[Gargas, Vohr, Tyson et al. Pediatrics 2009:112-121.]
This study looked at outcomes (both by gestational age and birthweight) of 5,250 children born weighing less than 1000 grams between 1998 and 2001 in NICHD study hospitals in the US.
"Unimpaired" was defined as Bayley Scale scores equal to or greater than 85, a normal neurological exam, normal vision, hearing, swallowing, and walking.
This study offers a new perspective on outcomes since "mild" (and sometimes "moderate")disabilities -- which most of us parents would consider fairly severe -- are lumped in with "normal", "unimpaired" outcomes when neonatologists and other professionals give outcome information to parents.
This is, as many of us have learned the hard way, highly misleading.
So the NICHD researchers set out to record just how many children were actually free of impairment by the criteria above, at age 18 to 22 months.
We parents also know that 18 to 22 months is much too early to determine some pretty devastating outcomes of prematurity -- autism, for example -- so even these numbers may be overly optimistic.
Here's what they found:
Less than 1% of children born weighing less than or equal to 500 grams survived to be normal(that is, "unimpaired" at 18-22 months).
From 501 to 600 grams it is about 5% unimpaired;
701-800 grams about 15 % unimpaired ;
increasing to 24% for infants 901-1000 grams.
By gestational age: <1% at 23 weeks are unimpaired;
< 5% at 24 weeks;
about 15% at 25 weeks, and
about 24% at 27 and 28 weeks.
(I'm reading some of this from a graph so I can't cite exact percentages.)
After 27-28 weeks gestational age, infants born at 1000 grams or less are small for gestational age as well as premature -- an additional risk factor -- and the percentages of unimpaired decline again, so that, for example, less than 20% of children born at 31 weeks weighing 1000 grams are unimpaired.