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Clinical research: Birth complications increase autism risk

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Jessica Wright
4 February 2014

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Breathing help: Premature babies who require the use of a high-frequency ventilator have double the risk of developing autism relative to premature babies who do not.

In premature infants, bleeding inside the skull and respiratory distress requiring a certain type of ventilator may each contribute to an increased risk of autism, suggests a large study published in the January issue of The Journal of Pediatrics1.

The study looked at nearly 200,000 infants born prematurely in a group of Northern California hospitals run by Kaiser Permanente, an integrated insurance and hospital network. As in prior studies, the researchers found that the rate of autism increases with every week short of 37 weeks of gestation.

The researchers identified 2,462 children who had at least one insurance code designating an autism diagnosis. More than half of these children had been diagnosed on the basis of an in-person clinical assessment.

Of the 2,462 children, 280 were born prematurely. The autism prevalence among children born with typical gestation (37 to 41 weeks) is 1.2 percent. This prevalence rises to 2 percent for those born at 27 to 33 weeks of gestation and to nearly 4 percent for those born at less than 27 weeks of gestation.

What was unclear, however, is whether it is the prematurity itself or complications that raise the risk of autism. In the new study, the researchers were able to use the detailed hospital records to look at the overall health of the infants. 

Several medical factors showed no association with autism, the study found. These include a gastrointestinal disease common in premature infants, called necrotizing enterocolitis, the presence of bacteria in the blood and the need for resuscitation, using either chest compressions or epinephrine. 

In contrast, mild bleeding in the skull nearly doubled the risk of autism in premature infants, and severe bleeding increased the risk more than threefold. The use of a mechanical ventilator, which assists or replaces natural breathing, is not linked to an increased risk of autism. However, high-frequency ventilation — used for severe respiratory distress and when conventional ventilation does not work — increased risk about twofold.

Prematurity raises the risk of autism even when these factors are controlled for, however, suggesting that these complications do not wholly account for the increased risk. 

News and Opinion articles on SFARI.org are editorially independent of the Simons Foundation.

References:

1: Kuzniewicz M.W. et al. J. Pediatr. 164, 20-25 (2014) PubMed

Comments

Name: Amanda
4 February 2014 - 5:24PM

Is there anything at all surprising here? Premies are at increased risk for every imaginable developmental disorder.
As the parent of a mother of s severely affected son with ASD, who received excellent early intervention, which was sadly minimally effective, I wish there was more research on treatment. The vast majority of ASD moms had typical pregnancies, were under 35 and did not deliver premies.

Name: Sam
5 February 2014 - 2:09PM

Same old stories always going around the circle with same old approach to an autism epidemic.

Name: Eileen Simon
6 February 2014 - 12:44AM

Complications at birth are well recognized as part of the medical history of children with autism. What is most feared about a difficult birth? Oxygen insufficiency.

Research was done decades ago that should have been recognized as a possible cause of developmental language disorders. I will continue to point out an article in the October 1969 issue of the Scientific American in which monkeys subjected to asphyxia at birth were found to have damage in nuclei of the auditory pathway. If research published in 1969 is too old, these experiments should be done again. Now the brain can be examined with fMRI without having to “sacrifice” the animals used for research.

Asphyxia??? The method used 40 to 50 years ago is now (since the mid 1980s) a standard obstetric procedure, clamping the umbilical cord immediately after birth, whether or not the baby has begun breathing. A complicated resuscitation protocol is used for the 1 in 10 infants who do not breathe after the cord is clamped. Compare this statistic to that for autism. The need for resuscitation implies the infant has suffered some degree of asphyxia.

There is no health benefit from clamping the cord. This procedure should be stopped.

Name: Sam
6 February 2014 - 6:04PM

Seriously!!!

Asphyxia at birth doesnt explain why kids regress at 18 months to 24 months into autism. We know of a very clear group of children who regress into autism following normal infancy growth.

If this theory of yours had any basis, you would have seen much more autism cases before 1960s. Leo Kanner had to practically go around the work to find his first 12 cases. Oh please lets spend another 10 years researching this garbage theory. It seems as if they do it on purpose to never tackle autism head on, but rather come on with different angles therory to submerge the public (sheeps) head into Sand, as to keep them blind.

Name: Eileen Simon
6 February 2014 - 8:05PM

Autism has many causes. All causes must affect systems in the brain that prevent normal language development and lead to repetitive movements (stimming or chorea, and/or athetosis).

Nuclei in the brainstem auditory pathway have higher blood flow than any other area of the brain. This was reported in a seminal paper by Seymour Kety in 1962, and is free online via PubMed. The finding of damage by asphyxia is related to the high blood flow in these nuclei of the auditory system.

High blood flow makes the auditory system more vulnerable also to toxic substances that get into the circulation. The basal ganglia are also centers of high blood flow and are also sites of damage caused by oxygen insufficiency and bilirubin at birth or in the neonatal period.

Autistic regression may occur following illness in infancy that likely also injures the same vulnerable subcortical sites. Prenatal rubella infection has long been associated with developing autism.

Injury to subcortical systems before or during birth, or during early infancy, will prevent normal maturation of target sites like the language areas in the cerebral cortex.

Clamping the umbilical cord immediately after birth is a protocol adopted in the mid 1980s, about the same time that the vaccine schedule was increased. Before that, in Kanner’s day, textbooks of obstetrics taught that the cord should not be tied (or clamped) until pulsations in it ceased. Pulsations of the cord provide evidence of ongoing fetal circulation to the placenta, which cease once blood has been redirected to the lungs, and fetal valves in the heart have closed.

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