Health Care Zone

Obese Mothers More Likely to Have Children With Autism?

A new provocative study shows that compared to healthy-weight mothers, obese women are 67 percent more likely to have a child with autism. They were also about twice as likely to have a child with another developmental disorder.

Can autism be preventable? Scientists say, yes. And autism research points to early diagnosis and intervention — as early as when the child is eight months old — as the best way to stop this disabling brain disorder in its tracks.

But really being able to prevent autism requires a complete understanding of its causes — and scientists are still putting together that picture, despite intensive research for many decades.

Although the exact causes of autism are not known, scientists believe genetics is responsible for over half of the risk of a child developing autism and new research suggests multiple genetic mutations make a child susceptible for the disorder. The remaining half involves factors that include older parental age, premature birth or failure to take prenatal vitamins. Exposure to chemicals and other agents that can cause birth defects have also been shown to cause autism.

In recent years, scientists have also been looking for environmental triggers that push the children who are genetically prone to autism to actually go on and exhibit the social and communication skills problems that characterize the disorder — repetitive behaviors like rocking back and forth, trouble speaking, interacting with others or socializing and making friends with peers.

As the search for these triggers continues, new research from the University of California Davis MIND (Medical Investigation of Neurodevelopmental Disorders) Institute suggests that obesity may be one of those triggers.

To be more precise, the authors of the latest research say that, compared with healthy-weight mothers, women who are obese during their pregnancies are significantly more likely to have a child with autism and other developmental disorders.

Obesity and diabetes during pregnancy may be risk factors for autism spectrum disorder (ASD) and other neurodevelopmental problems in childhood, the new study of more than 1,000 children and their mothers concludes.

The authors say it’s the first study to examine the link between neurodevelopmental disorders and maternal metabolic conditions. Their findings are published in the May issue of the journal Pediatrics.

The authors warn that the findings could have serious public-health implications, given the ever-rising worldwide rates of obesity — and obesity in women of childbearing age. The link between obesity and developmental disorders is particularly worrisome because obesity has become so prevalent:
• In the United States, nearly 60 percent of women of childbearing age (20 to 39) are overweight and one-third are obese.
• According to Statistics Canada, 29 per cent of Canadian women are overweight and 23 percent are obese.
• According to the European Commission, obesity rates have more than doubled over the past 20 years in most European Union countries and over half the EU adult population is now classified as overweight or obese. The UK has the worst obesity rate in Europe with nearly one in four adults now classified as obese.
• There are an estimated 502 million obese adults worldwide, and the obesity epidemic is sweeping into low and middle-income countries, the World Health Organization’s obesity center reported in 2011.
• Obesity rates have been climbing fastest for women 25 to 34 years old, nearly doubling in the past 25 years.

The new findings follow a recent announcement by the U.S. Centers for Disease Control and Prevention announcement that autism-spectrum disorders affect one in 88 U.S. children, up from one in 110 in a 2009 report. The findings also add to the increasingly complex picture of possible factors that contribute to the disorders.

The UC David MIND researchers started out knowing that while autism’s cause is unknown, previous research suggests that its “pathogenesis” — or the chain of events leading to the disorder — most likely begins in the womb. This prompted them to wonder if there was a link between autism and maternal metabolic disorders.

“Over a third of U.S. women in their childbearing years are obese and nearly one-tenth have gestational or type 2 diabetes during pregnancy,” Paula Krakowiak, a biostatician with the MIND Institute tells CNN Health. “Our finding that these maternal conditions may be linked with neurodevelopment problems in children raises concerns and therefore may have serious public-health implications.”

For their study, the researchers from the UC David MIND — as well as the Vanderbilt University — analyzed data from children two to five years old born in California and enrolled in the CHARGE (Childhood Autism Risks from Genetics and the Environment) Study between January 2003 and June 2010.
• The children were between 24 and 60 months old
• 517 children who had autism
• 172 with other developmental disorders
• 315 children who were developing normally — the were used as the “controls”

The investigators used telephone interviews and medical records to gather information about the mothers, such as the mother’s age at delivery, education level, health status and other factors. This is what they found:
• 21.5 percent of the mothers of autistic children — and 23.8 percent of mothers of children with another developmental disorder — were obese
• 14.3 per cent of mothers of normally developing children were obese
• Or, expressed in another way, compared to healthy-weight mothers, obese women were 67 percent more likely to have a child with autism. They were also about twice as likely to have a child with another developmental disorder.

Compared with the “control” mothers, mothers of children with autism or other developmental disorders also have diabetes and high blood pressure — aside from obesity. Excess weight increases the risk of women developing diabetes during pregnancy.

Diabetes matters
The researchers also found that:
• Compared with mothers who had healthy weight during pregnancy, mothers with diabetes were also found to be twice as likely to have a child with developmental delays.
• Compared to autistic children born to mothers of healthy weight during pregnancy, autistic children born to diabetic mothers had greater deficits in communication skills.
• Compared to the non-autistic children of healthy women, children who were not autistic — but had diabetic mothers — also showed some signs of socialization problems as well as poor communication skills.

“That in itself was a surprising finding,” said Krakowiak, who is a PhD candidate in epidemiology with the MIND Institute.

Why does this happen?

How a mother’s weight or metabolic disorders during pregnancy might contribute to autism or other problems isn’t known. But the researchers surmise that this happens because obesity has been linked to inflammation and obese pregnant women have higher levels of inflammatory chemicals circulating in their blood. These can cross the placenta and have been shown — in animal studies, at least — to disrupt normal fetal brain development.

What’s more, “if a mom’s blood sugar spikes up and down beyond the normal ranges maternal glucose can cross the placenta,” Krakowiak tells Canada.com. When this happens, the fetus has to compensate by producing additional amounts of insulin. But insulin can be a growth factor — and more of it can cause the baby to grow faster. “And when a baby is growing at a faster rate it needs to use additional amounts of oxygen,” she says. If there isn’t enough oxygen available, low blood oxygen levels can affect a baby’s brain development.

Another possibility is that insulin resistance is involved, says Dr. Irva Hertz-Picciotto, senior author of the study and chief of the environmental and occupational health division in public health sciences at UC Davis.

When insulin isn’t made or used properly by the body — as can be the case in some obese people — it alters how sugar, which serves as energy for the body, is produced and transported to tissues including the brain. Such disruption may have a impact fetal brains powerfully, as these brains are known to need a lot of sugar.

But the researchers weren’t able to compare mothers who had well-controlled blood sugar to those who didn’t, she notes.

“The brain is quintessentially susceptible to everything’s that happening in the mother’s body,” says Dr. Hertz-Picciotto.

Still, the study doesn’t prove cause and effect, Krakowiak stresses. And more research is needed to prove this association between obesity and other metabolic conditions during pregnancy and autism further.

Obesity and metabolic factors in pregnant women just the last in a growing list of potential causes of autism.

Last year, the UC Davis researchers had investigated other environmental factors like pollutants, and, using data from the same children in the CHARGE study, found that the risk of autism doubled if families were living closer to a freeway during the third trimester of pregnancy.

Health experts say these factors seem to contribute to autism:
• Obesity among mothers
• Older parental age
• Premature birth/birth complications
• Fewer than 12 months between children

These factors are suspected and are under investigation:
• Environmental toxins
• Diet and other lifestyle factors
• Other existing medical conditions, including viral infections

Provocative
Calling the findings ‘provocative,’ Dr. Hyman, who heads the American Academy of Pediatrics’ autism subcommittee and who wasn’t involved in the study, says that although the observational study can’t prove a causal relationship, the findings still suggest that maternal metabolic disorders contribute to autism and other developmental disorders.

In an interview with MedPage Today, she notes that other factors related to obesity that were not captured in the database could also be involved in the relationships. All of these explanations are hypothetical and need to be studied further.

But she advises moms of autistic children to focus more on effective interventions than on what caused the autism. Mothers of children with disabilities often scrutinize everything they did, ate, and were exposed to during their pregnancy to try to find an explanation. But, she points out, “At the time of your child’s diagnosis, that’s all ancient history. What you have to concentrate on is what you can do, what are effective interventions … being proactive and changing what you can change (that’s) really what research is all about. It’s not about pointing fingers.”

Modifiable behavior
Study author Krakowiak agrees. “I would definitely not want moms to feel guilty for having any one of these conditions and that being a cause of their child’s disorder,” she says.

“I think that we have to look at this as a call to our society,” she says, “that (shows) there are multiple implications of the obesity epidemic that we need to consider.”

“And that we need to be proactive in what we can do,” she adds. “There are so many things we can’t change. We can change this.”

“What we can do is we can eat healthy and exercise, and this is a positive suggestion for change,” she tells MedPage Today.

Dr. Hyman agrees with this positive theme in the results. “The statistics on obesity are alarming, but it’s a modifiable risk factor,” she concludes.

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