Low Birth Weight and Preterm Birth: Autism Risk Factors?
June 2, 2008 by Kristina Chew, PhD
Filed under Health
A new study in Pediatrics links low birth weight (less than 5.5 pounds) and preterm birth to an increased risk for autism in infants by about twofold, and more so in girls than in boys. From an overview at CBS.com:
When the 565 boys and girls with autism were looked at separately, the boys had less than a twofold increased risk of autism if they were born at low birth weight, but the low-birth-weight girls had a threefold or higher risk, found [Diana] Schendel [PhD, lead health scientist at the National Center on Birth Defects and Developmental Disabilities at the CDC] and her CDC colleague Tanya Karapurkar Bhasin, MPH.
They also found that low birth weight (less than 5.5 pounds) and early preterm birth (less than 33 weeks’ gestation) affected groups of children differently, depending on whether they had autism alone or autism and other developmental disabilities.
“There may be a lot of variation in the endpoint we call autism,” Schendel tells WebMD. The study result, she says, “really is highlighting that we aren’t looking for one cause of autism .” The study builds on previous research, some of which has also found a link between low birth weight and autism.
Anecdotally: My son was full-term and 8 lbs, 3 oz. A relative had a baby (a girl) a few weeks before Charlie was born; she was under lbs and a few weeks early. She met every developmental milestone very much on time and Charlie has been delayed in almost everything. And, Charlie has autism.
I’m always curious about the criteria used to select subjects. I know we are not eligible for many b/c of the overlapping disabilities, extremely low birthwt (18.7 oz) and extreme prematurity (27 wks). What studies (if you are aware) have been done using data about extremely premature and tiny babies? Or do they just seem to be “written off” as nearly guaranteed to have significant developmental issues?
Nicholas was 2 weeks overdue and weighed 9 pounds 9 ounces.
By contrast, my cousin had a preemie a few months later born 5 weeks early who weighed just over 5 pounds and is developmentally typical (and actually a bit advanced for her age.)
So, another potential risk factor but along with other things, not causation. I had already known that a premie could be at greater risk for CP, some neurologic disorders or LDs, but not necessarily to develop them, however the greater the prematurity, the greater the risk.
Eleanor was full term and 8 lbs. 5 oz, so it does not discount the above, just that she would not be among the sample.
“There may be a lot of variation in the endpoint we call autism,” Schendel tells WebMD. The study result, she says, “really is highlighting that we aren’t looking for one cause of autism .”
Seems like a reasonable point of view.
I notes those remarks by Schendel too, especially the notion of autism as an “endpoint.” My pregnancy was very healthy and I did “all the things” that were recommended.
@Niksmom, looking in pubmed, found:
“The Scottish low birthweight study: II. Language attainment, cognitive status, and behavioural problems.” Arch Dis Child. 1992 June; 67(6): 682–686.
http://www.pubmedcentral.nih.gov/articlerender.fcgi?tool=pmcentrez&artid=1793820
I was a preemie weighing 3 lbs back in 1960. Matt weighed almost 9 lbs and Nick was in the 7 lb range.
TH was 7 lb, 12 oz. Dubya was 8 lbs, 5. Little was 7 lbs 9 oz. No low birthweights here. Now, my niece was tiny and walked at seven months. Really. We’ve got the video.
I was 8 lbs, 4 oz. at birth, which is apparently not all that tiny…however, I’ve grown up to be a rather small adult (5′3″, 100 lbs). My siblings (neither of which is autistic, though they’re certainly quirky in their own ways) were around the same size. Doesn’t seem that birth weight had any correlation with neurological wiring in our family, at least…
All of mine were 6 lbs plus, smallish but not dangerously so, or so I thought.
I don’t remember my weight, other than I was the heaviest of two (my sister, not being biologically related, was lighter than me too, for whatever that’s worth). Wasn’t a preterm birth, either.
What makes this interesting for me, though, is the separation of statistics in terms of girls and boys. It brings up a lot of questions, so I need to take a closer look at the study as to the assumptions and creations.
I do like how Schendel brings up the “chicken-and-egg” question as to the fetus development; whether autism would cause lower birth weight or vice versa (or either, depending on a different condition in a similar skin). What is interesting about her analysis, though, is that while she posits a single condition, she posits several ways to get there. I’m not sure how I feel about that; especially if you’re dealing with factors like late-onset, why would you ever assume a single biological nature out of hand while recognizing that the means are so different?
Cliff
I was of normal size and weight at birth, and 2 weeks late. Second child (brother) was ridiculously huge at birth but on time. Third child (brother) was also big, though not quite that big, and also on time.
That study makes sense to me- there’s always seemed to be a higher rate of autism in triplets and up, which are pretty much alway pre-term. I’ve seen some studies done on the steroids done to help mature the babies’ lungs before birth as well as some of the meds given to prevent pre-terms later, although I don’t think that anyone’s come to any conclusions.
My kids were born at 30 weeks, 2.13, 2.14, and 3.4 pounds.
It’s the difference in gender the study notes that seems interesting—–perhaps some sort of marker for girls in particular.
Charlie was such a big baby relative to me that his birth weight was always notable. It was predicted that he’d be a lot smaller, actually.
Both my kids were born under 6 pounds. My daughter has autism and so far, at 18 months old, my son is developing typically.
I thought there was already some type of “given” that low weight babies (typically babies born pre-term) were at risk of developmental delays. Is this study different because it’s referring specifically to autism and/or because of the gender significance?
Someone emailed me yesterday with some anecdotal story of how a large amount of increased vitamin D supplements significantly increased a 7 year old little boy’s ability to communicate, his self-help skills and ability to interact in social settings. Obviously it’s not a study, but all these studies and stories are certainly interesting – how our bodies all respond individually and separately to various environmental factors given whatever predetermined predispositions we each carry with us.
My son was quite large, 8lbs. 15 oz., and was 2 days past his due date. In contrast, my best friend has 2 neurotypical girls. Both were born around 38 weeks’ gestation, both weighed 5lbs. 13 oz..
Meh. More junk science, in my opinion.
Hello friends –
Being a lower birth weight tends to make you more likely to suffer from a wide range of complications; neurological or otherwise. It is for this reason, that premature children are exluded from studies measuing outcomes of children exposed to different levels of certain vaccine preservatives.
I was 3.3 pounds at birth and not given much chance to survive. Ha!
- pD
Still pondering this over here…
I wonder what, if any, significance was given to the actual preganancy factors. e.g., single artery-single vessel cord, IVF or other fertility enhancement vs. natural conception, maternal age, other outstanding gestational characteristics —diabetes, HELP, placenta previa, etc…
It just seems to me that there are so many variables that there may never be a single answer.
….and I had 4 premature babies, weighing 2.1-2.10 lbs., only one has autism….and they all had mmr vaccines…only one has autism…
years ago I asked an expert if prematurity had anything to do with autism…the answer was emphatically no…now they say yes…maybe…it boggles the mind
xR
@pD,
Ha!
@ASDmomNC,
Your son’s size compared to that of his sisters reminds me of Charlie’s birthweight and length relative to my cousin’s girl (she is a 1st cousin). Charlie also had really long limbs from the time he was born and was just kind of uncoordinated, whereas my cousin’s daughter was small and compact.
My twins were both under five pounds, and born at 32 weeks. We also have autism on both sides of the family, so they got a double-whammy of risk-factors!
Autism in my husband’s extended family and mine too so some sort of “whammy” for Charlie!
on the gender differences, maybe this goes back to the invisibility of autism in girls… people are paying more attention to possible issues in low birthweight babies?
oh, and my autie boy was induced, as he was late, and was a healthy 9lbs, 1 oz.
my son was induced as I’d been in labor for over 20 hours.