Linking Autism to Birth: Two Studies Find that the Environmental Conditions of Pregnancy Effect the Prevalence and Severity of Autism Symptoms

April 09, 2012

Linking Autism to Birth: Two Studies Find that the Environmental Conditions of Pregnancy Effect the Prevalence and Severity of Autism Symptoms

[caption id="attachment_1334" align="alignleft" width="300" caption="Image courtesy of imagerymajestic"][/caption] In our continued coverage of Autism Awareness Month news, I want to share two studies that I found this morning that deal with different aspects of pregnancy and childbirth, and their links to both autism diagnosis and the severity of the disorder as a child ages. Though the root cause of autism is thought to be related to genetics, there is also a strong environmental influence. Because of this, studies into the ways in which early environment effect the rate of autism diagnosis are an important step in continuing to understand, prevent and treat this disorder now affecting 1 in 88 children. The first report comes from NPR News’ Health Report and discusses a new study from the journal Pediatrics. The study, which looked at 1,000 mothers whose children were diagnosed with either autism or some other developmental disability found that maternal obesity, diabetes, and high blood pressure contribute to a higher rate of autism and related diagnosis in children. The theory, as the report covers, has to do with the environmental factors present in utero for such children. The fear, as the NPR report posits, is that with obesity rates on the rise in the U.S. and globally – fully one of three women of childbearing age are considered medically obese – that the 1 in 88 rate of autism will continue to rise as well. The next report is from a study conducted by researchers at Michigan State University and published in the Journal of Autism and Developmental Disorders. The study, formally titled “The Effect of Gestational Age on Symptom Severity in Children with Autism Spectrum Disorder,” is the first to look at the impact that the age at birth has on autism diagnosis on a wide-scale. That is, while it has long been acknowledged that preterm babies are more likely to receive a diagnosis of autism spectrum disorder, this study extended that overview to include very preterm babies (born before 34 weeks), preterm babies (born between 34 and 37 weeks), standard gestation babies (between 37 and 42 weeks), and post-term babies (born after 42 weeks). The findings reveal that both preterm and post-term births positively affect the rate of autistic diagnosis. This has lead researchers to continue to explore the role that this early environmental factor plays in autism diagnosis, looking both at the causes of preterm and post-term birth as well as looking towards prevention methods surrounding this particular risk factor. Study Warns of Autism Risk for Children of Obese Mothers From NPR News’ Health Report Scientists have found one more reason that pregnancy and obesity can be a bad combination.
A new study in the journal Pediatrics suggests that moms who are obese or have diabetes are more likely to have a child with autism or another developmental problem. The finding is "worrisome in light of this rather striking epidemic of obesity" in the U.S., says Irva Hertz-Picciotto from the MIND Institute at the University of California, Davis, one of the study's authors. But it's not clear whether there's any connection between rising obesity rates and the increasing number of children diagnosed with autism, she says. The new study looked at about 1,000 mothers. Half of them had a child with an autism spectrum disorder, while the rest had a child with a developmental delay unrelated to autism, or no developmental problem. Researchers wanted to know whether autism was more likely if a woman was obese, diabetic or had high blood pressure during pregnancy. "We found that if women had one of these three conditions, the increased risk for her child was about 60 percent," Hertz-Picciotto says, though the overall risk was still relatively small. These conditions also more than doubled the chance that a child would have some other developmental delay. Obesity was the most common risk factor, affecting more than 20 percent of mothers with an autistic child. Also, obesity increases the risk that a woman will have diabetes during pregnancy, and can also increase the risk for high blood pressure. "Obesity really affects the mother's physiology aside from the fact that she's carrying around a lot of extra weight," Hertz-Picciotto says. The results also suggest that both obesity and diabetes are affecting early brain development, she says. That could be because these conditions are associated with inflammation in developing tissues, including those in the brain, she says. Another possibility is that obesity and diabetes are reducing the nutrients reaching the fetus by reducing the body's ability to use insulin, she says. "We're talking about a fetal brain that could be suffering from a lack of oxygen," she says. In the U.S., about one-third of women of child-bearing age are obese, and one child in 88 now has an autism spectrum disorder, according to government statistics. So it's clearly a good idea for women who are overweight or obese to try to slim down before becoming pregnant, Hertz-Picciotto says. But she says people shouldn't assume that any particular child developed autism because of his or her mother's weight.
Children with Autism Suffer More Severe Symptoms When Born Either Preterm or Post-Term Press Release from Medical News Today For children with autism, being born several weeks early or several weeks late tends to increase the severity of their symptoms, according to new research out of Michigan State University. Additionally, autistic children who were born either preterm or post-term are more likely to self-injure themselves compared with autistic children born on time, revealed the study by Tammy Movsas of MSU's Department of Epidemiology. Though the study did not uncover why there is an increase in autistic symptoms, the reasons may be tied to some of the underlying causes of why a child is born preterm (prior to 37 weeks) or post-term (after 42 weeks) in the first place. The research appears online in the Journal of Autism and Development Disorders. Movsas, a postdoctoral epidemiology fellow in MSU's College of Human Medicine, said the study reveals there are many different manifestations of autism spectrum disorder, a collection of developmental disorders including both autism and Asperger syndrome. It also shows the length of the mother's pregnancy is one factor affecting the severity of the disorder. While previous research has linked premature birth to higher rates of autism, this is one of the first studies to look at the severity of the disease among autistic children who had been born early, on time and late. "We think about autism being caused by a combination of genetic and environmental factors," she said. "With preterm and post-term babies, there is something underlying that is altering the genetic expression of autism. "The outside environment in which a preterm baby continues to mature is very different than the environment that the baby would have experienced in utero. This change in environment may be part of the reason why there is a difference in autistic severity in this set of infants." Movsas added that for post-term babies, the longer exposure to hormones while a baby is in utero, the higher chance of placental malfunction and the increased rate of C-section and instrument-assisted births may play a role. The study also found that babies born outside of normal gestational age (40 weeks) - specifically very preterm babies - showed an increase in stereotypical autistic mannerisms. "Normal gestation age of birth seems to mitigate the severity of autism spectrum disorder symptoms, and the types of autistic traits tend to be different depending on age at birth," she said. The study analyzed an online database compiled by Kennedy Krieger Institute at Johns Hopkins University of nearly 4,200 mothers - with autistic children ages 4-21 - between 2006 and 2010. It divided the data on births into four categories: very preterm (born prior to 34 weeks); preterm (34 to 37 weeks); standard (37 to 42 weeks); and post-term (born after 42 weeks) The mothers filled out a pair of questionnaires regarding the symptoms of their autistic children, and the results revealed very preterm, preterm and post-term autistic children had significantly higher screening scores for autism spectrum disorder than autistic children born full term. "The findings point to the fact that although autism has a strong genetic component, something about pregnancy or the perinatal period may affect how autism manifests," said Nigel Paneth, an MSU epidemiologist who worked with Movsas on the paper. "This adds to our earlier finding that prematurity is a major risk factor for autism spectrum disorder and may help us understand if anything can be done during early life to prevent or alleviate autism spectrum disorder."



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