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
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.”
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.