Diabetes, Obesity During Pregnancy May Up Autism Risk
With commentary by study author Xiaobin Wang, ScD, director of the Center on the Early Life Origins of Disease and the Zanvyl Krieger professor in child health, Johns Hopkins Bloomberg School of Public Health, Baltimore, and Cheryl Walker, MD, associate professor of obstetrics and gynecology, MIND Institute, University of California, Davis.
The risk of autism may increase substantially for children born to mothers with diabetes who are also obese, new research finds.
"Children born to obese women with diabetes had about four times the risk of autism spectrum disorder (ASD) compared to that of children born to mothers of normal weight and without diabetes," says Xiaobin Wang, ScD, director of the Center of t he Early Life Origins of Disease and the Zanvyl Krieger Professor of Pediatrics, Johns Hopkins Bloomberg School of Public Health.
While previous research has found that maternal diabetes is linked with an increased risk of autism spectrum disorders, and other studies have found obesity is also a risk favor, ''ours is the first to look at both together," Wang says.
The study is published in the journal Pediatrics.
Autism spectrum includes a range of neuro-developmental conditions. All are marked by deficits in socialization, verbal and non-verbal communication and repetitive behaviors. About 1 in 68 U.S. children are now diagnosed with ASD, according to the U.S. Centers for Disease Control and Prevention.
Focusing on the Risks
Wang and her colleagues looked at more than 2,700 mother-child pairs, enrolled in the Boston Birth Cohort study between 1998 and 2014. The researchers looked at data on the mothers' weight before pregnancy and whether they had diabetes before becoming pregnant or whether they developed it during pregnancy, known as gestational diabetes. While the researchers did not have specific information on whether the pre-pregnancy diabetes was type 1 or type 2, Wang says most were likely type 2. (Type 1, in which the body does not produce insulin to regulate blood sugar, is typically diagnosed earlier in life than type 2, in which the body does not produce enough insulin or use it effectively enough.)
The researchers followed up the children, from time of birth through childhood, looking at electronic records or information from visits. They found 102 children who received an ASD diagnosis. The diagnosis was more likely, they found, if the mothers were obese or had diabetes.
Being obese without diabetes raised the risk of an autism diagnosis slightly, Wang found, and so did having diabetes without being obese. The combination is what raised the risk significantly, she says.
"Put it together and it is a three to four fold increase," she says, compared to mothers who are not obese and do not have diabetes. "There is an additive effect." About half, or 49, of the 102 children diagnosed with ASD also had intellectual disabilities, Wang found.
Perspective on Findings
"These findings add to the list of concerns faced by women contemplating pregnancy who are obese and/or have diabetes mellitus," says Cheryl Walker, MD, associate professor of obstetrics and gynecology at the MIND Institute, University of California Davis. She reviewed the findings.
Researchers at UC Davis previously reported on the obesity and autism link, Dr. Walker says. The new study extends the findings to include the risk of diabetes, she says.
Explaining the Link
Wang and her team found a link or association, but cannot prove cause and effect. She cannot explain with certainty why obesity plus diabetes increases the autism risk in children, she says. She and others speculate on several possible explanations. "Obesity and diabetes can lead to inflammatory responses," Wang says, and that may lead to fetal brain inflammation, hurting development.
"The developing fetal brain is extremely delicate," Dr. Walker says. Even subtle changes in a mother's physiology or how the placenta function can lead to alterations in the baby's brain development, she says.
High blood sugar levels may also be hard on the fetal brain. High blood sugar can cause oxidative stress, and that can be harmful, too, Dr. Walker says.
Advice, Insight for Women Before, During Pregnancy
While the risk found is substantial, most of the children in the study did not develop ASD. The researchers also cite a limitation of the study, saying some of the children may have only had a tentative ASD diagnosis or may have been misclassified.
The study does, however, suggest several actions for women who are pregnant or are contemplating it, Wang and Dr. Walker say. For women contemplating pregnancy, Dr. Walker says, normalizing weight before conceiving is advised. Women who already have diabetes should work with their doctor to bring it under good control, she adds.
Families who already have one or more children with ASD face a higher risk, in general, of having another child with ASD, says Dr. Walker. Likewise, these women should work to bring their weight under control before trying to conceive, she says. If they have diabetes, they should bring it under control before conceiving, she says.
Women who don't have diabetes when they become pregnant should be screened to be sure they don't have gestational diabetes, Wang says. Screening is recommended after 24 weeks by the U.S. Preventive Services Task Force. Women could ask their doctor about earlier screening, Wang says.