Autism Linked to Mom's Diabetes

Mothers who are obese or who have diabetes appear to be more likely to have children with neurodevelopmental disorders, including autism.... According to Paula Krakowiak, MS, a PhD candidate at the MIND Institute at the University of California Davis, and colleagues, maternal obesity was associated with greater odds of the offspring receiving a diagnosis of an autism spectrum disorder (OR 1.67, 95% CI 1.10 to 2.56) or a developmental delay (OR 2.08, 95% CI 1.20 to 3.61) by age 5. A combination of maternal metabolic conditions was associated with a range of impairments in the children's development, the researchers reported. Susan Hyman, MD, of the University of Rochester in Rochester, N.Y., who is the chair of the American Academy of Pediatrics' autism subcommittee, called the findings provocative. Although the observational study could not prove causal relationships, Hyman said the findings suggest that maternal metabolic disorders are contributing causes to autism and other developmental disorders. Roughly one in every 88 children has an autism spectrum disorder (ASD), according to a recent estimate from the CDC, and one in every 83 has another developmental delay. Hyman also said that if maternal metabolic conditions are adding to the burden of autism, it is likely a small contribution. She noted that other factors related to obesity that were not captured in the database could be involved in the relationships. She added that 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 said, "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 is really what research is all about. It's not about pointing fingers." Krakowiak agreed, noting that the study is preliminary and cannot prove cause and effect; it is possible there are other factors involved that independently affect obesity and autism. "So 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 said. The exact cause of autism has not been identified, but both genetics and environmental factors are believed to be involved. Previous studies have identified an association between diabetes during pregnancy and general developmental impairments in the offspring, although research examining the relationship with autism has yielded mixed results. To further explore issue, Krakowiak and colleagues turned to the CHARGE (Childhood Autism Risks from Genetics and the Environment) study, an ongoing case-control study of children born in California. The current analysis included 1,004 children ages 2 to 5 -- 517 with an autism spectrum disorder, 172 with other developmental delays, and 315 with typical development. All of the children were evaluated using the Mullen Scales of Early Learning (MSEL) and the Vineland Adaptive Behavior Scales (VABS), which assessed cognitive and adaptive development, respectively. The specific metabolic conditions assessed among the mothers were obesity, hypertension, and diabetes (either gestational diabetes or type 2 diabetes) during pregnancy. All three of the metabolic conditions were more frequent among the mothers of children with an ASD or other developmental delay. Combined, the rates were 28.6% for mothers of children with an ASD, 34.9% for mothers of children with a developmental delay, and 19.4% for mothers of typically developing children. After adjustment for sociodemographics and other factors, mothers who had one of the three conditions were more likely to have a child diagnosed with an ASD (OR 1.61) or developmental delay (OR 2.35). Maternal hypertension alone was not related to either outcome, and maternal diabetes was associated with greater odds of having a child with a developmental delay (OR 2.33), but not autism. Maternal obesity was associated both with ASD and developmental delay among the children. Among the children with an ASD, maternal diabetes was associated with "relatively small" impairments in expressive language. Among the children without an ASD, the combination of maternal conditions was associated with a wide range of deficits in cognition and adaptive development. Although a case-control study cannot prove cause and effect, there are some possible mechanisms to explain a relationship between maternal metabolic conditions and a child's neurodevelopment, according to Hyman. Maternal glucose, but not insulin, can cross the placenta. If the mother has elevated levels of glucose, the fetus will have to produce more insulin. The increased oxygen demand that results can induce intrauterine tissue hypoxia. Poorly regulated maternal glucose could also result in iron deficiency in the fetus. Both hypoxia and iron deficiency can harm the developing brain. An alternate explanation is that the proinflammatory cytokines present in mothers with metabolic conditions may impair fetal neurodevelopment. Hyman said all of these explanations are hypothetical and need to be studied further. "I think that we have to look at this as a call to our society that 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 said. "What we can do is we can eat healthy and exercise, and this is a positive suggestion for change. There are so many things we can't change. We can change this."