In today’s Pediatrics, researchers at Johns Hopkins Bloomberg School of Public Health report that they found a three- to four-fold higher rate of autism among children born to women who were both diabetic and obese during pregnancy.
The findings raise many questions and concerns. To provide perspective, we talked with epidemiologist Michael Rosanoff and developmental pediatrician Paul Wang. Dr. Wang is Autism Speaks’ senior vice president for medical research. Mr. Rosanoff is Autism Speaks’ director for public health research.
Q: Too often, this type of finding is taken as implying parents are somehow to blame for their children’s autism. Why would you urge against such an interpretation?
Michael Rosanoff: Autism is a complex condition caused by a combination of environmental and genetic factors. By environmental, researchers mean a broad range of nongenetic influences including maternal health and conditions in the womb. No one environmental factor causes autism by itself. So when we say an environmental factor increases the risk of autism, we are not saying that it causes autism. In other words, not all moms who are both diabetic and obese will have a child with autism. In fact, the vast majority will not.
Paul Wang: We welcome research that helps us identify some of the factors that increase the risk that autism will develop. But as Michael suggests, the vast majority of children exposed to these risk factors do not develop autism. Except in rare cases, it's not possible to say exactly why a particular child has the condition. Parents certainly shouldn’t blame themselves when the scientific understanding is so nebulous – and when so many of autism’s risk factors are beyond their control.
Q: The researchers found a significant increase in autism risk only when diabetes and obesity occurred together during pregnancy. Does this answer some questions raised by previous research looking at obesity or diabetes separately?
MR: The children of moms who were either obese or had diabetes did not have a significantly increased rate of autism in this study. This counters some previous research that had shown a slight increased risk of autism among children of mothers who were either obese or diabetic during pregnancy.
The significant risk, according to this study, was when obesity and diabetes coincided during pregnancy. Moms who were obese and had diabetes going into pregnancy – that is, they had preexisting diabetes – were four times more likely to have a child with autism than were moms who had neither condition. Obese moms who developed diabetes during pregnancy – what we call gestational diabetes – were three times more likely to have a child with autism.
But because research methods differ between studies, we can’t directly compare these findings to those of previous studies. Scientific research requires retesting and replication. When results are replicated enough, it increases our confidence that the results are correct. In this case, we see growing evidence that obesity and/or diabetes during pregnancy may increase risk for autism. But how high of an increased risk and exactly what causes the increased risk remains unclear.
Q: The researchers suggest that their findings implicate inflammation during pregnancy as increasing autism risk. Why would that be and is it important?
PW: While several studies now implicate obesity and diabetes as risk factors, we still don't know exactly how these conditions might end up contributing to autism. Two possibilities that the authors mention are inflammation and oxidative stress – both of which can affect early brain development.
What’s more, the suggestion that diabetes during pregnancy causes brain inflammation is from studies with animals. It's not definitively known if diabetes in a pregnant woman causes inflammation in her fetus’s developing brain. At the same time, we do know that other inflammatory conditions in pregnancy – such as an infections serious enough to require the mother’s hospitalization – are associated with increased risk for autism.
Q: What should prospective parents take away from these findings?
PW: These findings further support what we know well: that healthy pregnancies are important for healthy fetal and child development. We also know that attention to good health should start before pregnancy, with optimal nutrition and vaccination against diseases like influenza or rubella that can greatly increase the risk of autism if they occur during pregnancy.
Nutritional and weight management during pregnancy are certainly important. We also need further research to understand whether and how we can better support a woman’s pregnancy when conditions such as gestational diabetes or maternal infections arise.
MR: I echo Paul in emphasizing that these findings underscore the importance of optimizing a woman’s health during pregnancy. A healthy pregnancy is vital to healthy brain development and this goes far beyond the development of autism.
What is becoming increasingly clear is that the developing fetus may be particularly sensitive to a number of environmental factors during pregnancy – including maternal obesity and diabetes that may increase the risk of autism. It bears repeating: No one of these factors cause autism in and of itself.
Q: Finally, it’s very understandable for parents – especially parents who already have a child on the spectrum – to feel whipsawed by all the risk studies coming out. Why is this type of research important and what should we be taking from it without driving ourselves crazy?
PW: Science is a process, and sometimes it seems very slow and painstaking. But this is also the strength of science – researchers are constantly double-checking the findings of other researchers. They also build on previous research to improve experiments and design new experiments that address the fresh questions that arise during research. It takes decades to make progress against any complex condition or disorder. And autism certainly ranks among the most complex! With continued support for research, we will continue making progress on autism’s causes and treatments.
CBS News interviewed Dr. Wang for its coverage of the Pediatrics report. View the news segment here.