June 2, 2008
Autism Linked to Low Birth Weight
Study Shows Increased Risk of Autism in Low Birth Weight or Preterm Babies
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(CBS/iStockphoto)
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The research bolsters the suspected link between autism, low birth weight, and prematurity.
"We saw this difference in risk between boys and girls," says Diana Schendel, PhD, lead health scientist at the National Center on Birth Defects and Developmental Disabilities at the CDC in Atlanta. The gender finding was unexpected, she says, especially since autism is much more common in boys. Schendel is a researcher of the study, published in Pediatrics.
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 Schendel 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.
"What is new in this study is the in-depth look at the gender effect," she says. The analyses of different groups classified by number and type of disability also add new information.
Study Details: Autism and Low Birth Weight
The researchers examined the records of 565 children with autism, born in Atlanta from 1986 to 1993, matching them to a control group of children. They looked at whether the children were born early, small, or both, and whether they had autism and other developmental problems.
The children with autism were further divided into three groups: those who had autism but no other developmental disabilities, those with autism who also had an intellectual disability, and those with autism and more than one other developmental disability.
About one in 150 children in the U.S. now have autism or related disorders that fall on what is known as the autism spectrum, according to the CDC.
Overall, the researchers found that a birth weight below 5.5 pounds was associated with a 2.3-fold increased risk for autism. Although preterm birth earlier than 33 weeks was not statistically linked to autism for boys, there was a significant fivefold increased risk seen for girls with autism.
The researchers then looked at the subgroups, divided by type and number of disability, and found variations. For instance, the increase in risk for autism in low-birth-weight girls with mental retardation was fourfold, while the increased risk found in low-birth-weight boys just for developing autism was not statistically significant.
Schendel can't explain why the low-birth-weight girls were found to have a greater risk than the low-birth-weight boys. Both low birth weight and preterm birth are markers, she says, that something may have gone wrong during the pregnancy . The poor fetal growth resulting in low birth weight may be associated with developmental problems. Or, on the other hand, low birth weight may be a marker of a fetus that's already adversely affected neurologically, she says.
"We don't know if it's the low birth weight ... causing brain damage, or whether the brain damage has occurred and low birth weight is the consequence," she tells WebMD.
Second Opinion: Low Birth Weight and Autism
The study is scientifically solid, says Susan Hyman, MD, an autism researcher and an associate professor of pediatrics at the University of Rochester Medical Center,University of Rochester School of Medicine, N.Y. She chairs the autism expert panel of the American Academy of Pediatrics.
Though previous research has yielded conflicting findings about the low birth weight-autism link, "I think this study comes close to laying the debate to rest," Hyman says.
"Pediatricians are very aware to monitor babies [born prematurely or at low birth weight] that require neonatal intensive care unit care for any sort of developmental difficulties," she says. But autism has not been targeted specifically; this study may make them more aware, she says.
Under the academy's developmental surveillance guidelines, Hyman says, children born early and small should be monitored for developmental disabilities. And the academy recommends routine screening for autism at 18, 24, and 30 months and also when there are parental concerns, she says.
Advice for Future Parents
While there's no "cure" to avoid low birth weight, Schendel advises pregnant women to seek prenatal care as early as possible.
"Discuss with your doctor your lifestyle," she says. It's important, for instance, for pregnant women not to smoke cigarettes and to avoid infections, among other healthy lifestyle habits.
Hyman adds: "Don't smoke, don't drink. Take your vitamins. Eat well. Sleep enough. Moderate exercise [as recommended by your doctor] is good. And don't worry. Stress is bad for pregnant women."
By Kathleen Doheny
Reviewed by Louise Chang
©2005-2008 WebMD, LLC. All rights reserved.
The secrets of tennis legend 
You can''t make a blanket statement that older paternal age is the common denominator. My husband was 23 when our twins were born prematurely. I have many friends whose children have autism and who are, like my husband and I, in their late 20''s or very early 30''s.
Just because your children do not fit the criteria of being low birth weight or premature does not mean that this study is ***. They are not suggesting that EVERY child with autism has low birth weight or was premature. What they are suggesting is that there are SOME children who have been diagnosed with Autism who fit these criterion.
My twins just turned 7. They were born at 27 weeks (yes, 13 weeks early) and weighed less than 3 pounds each. Not until this year was one of them diagnosed with Aspergers. I suspected that it may have been due to his prematurity, but had never seen any data to back that up. My twins did not have vaccines at the normal times. In fact, they didn''t have their first vaccine until well after 8 months of age. And I was pro-active in making sure that the vaccines they got at that time were mercury-free.
This study does not negate your childrens diagnosis. You know by now that there is no "textbook case" of Autism and for many parents, there is no rhyme or reason as to why their child has it. Just because your children were born full-term and at a normal weight and still received a Dx does not mean that there won''t be a child (or children) who won''t be Dx because they were a preemie, or had a low birth weight.
Just because your children do not fit the criteria of being low birth weight or premature does not mean that this study is ***. They are not suggesting that EVERY child with autism has low birth weight or was premature. What they are suggesting is that there are SOME children who have been diagnosed with Autism who fit these criterion.
My twins just turned 7. They were born at 27 weeks (yes, 13 weeks early) and weighed less than 3 pounds each. Not until this year was one of them diagnosed with Aspergers. I suspected that it may have been due to his prematurity, but had never seen any data to back that up. My twins did not have vaccines at the normal times. In fact, they didn''t have their first vaccine until well after 8 months of age. And I was pro-active in making sure that the vaccines they got at that time were mercury-free.
This study does not negate your childrens diagnosis. You know by now that there is no "textbook case" of Autism and for many parents, there is no rhyme or reason as to why their child has it. Just because your children were born full-term and at a normal weight and still received a Dx does not mean that there won''t be a child (or children) who won''t be Dx because they were a preemie, or had a low birth weight.
It is possible that some susceptible infants, who also happen to be pre-term or of low birth weight, suffer harm due to the full dose of hepatitis vaccine given within 12 hours of birth, as is shown in this study.
Hepatitis infection can only occur at the time of delivery due to birth trauma if the mother is positive for hepatitis B. Unfortunately the CDC, rather than testing the mothers for hepatitis B before delivery and advising vaccination to only those newborns who are at risk, requires that every newborn be vaccinated.
The risk of hepatitis B is now 1.6 in 100,000. Why are we continuing to vaccinate every newborn with hepatitis B vaccine (containing Aluminum) when the majority of them have absolutely no risk of getting this infection at birth.
Maybe the article and study were bunk. Maybe not. Or maybe the truth is in the middle.
My son weighed 10 lbs 3 oz and was not premature.
We get the picture. We know it''s a genetic and hereditary disease but the studies need to be larger and for more time. I''d rather hear about a large, ongoing study to compare birth weight and Autism and wait for findings that a few forms filled out and the data released.
- by anniepema June 2, 2008 9:52 PM EDT
- Lowbirth weight is more common with older fathers, autism is more common with older fathers. Older paternal age is the common denominator. The DNA of sperm collect mutations and copy errors and imprinting errors with the father''s age. http://longevity-science.org/SundayTimes.pdf
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