Children may be more likely to develop autism if their mothers were diagnosed with diabetes early in pregnancy, a new study shows.
Researchers found that mothers-to-be who developed gestational diabetes — high blood sugar during pregnancy in women who have never had diabetes — by their 26th week of pregnancy were 63 percent more likely to have a child diagnosed with an autism spectrum disorder (ASD) compared with women who did not have gestational diabetes at any point during their pregnancy (and who also did not have type 2 diabetes prior to pregnancy).
However, the authors emphasized that their findings do not mean that autism is common among children born to women who had gestational diabetes.
“Autism is still rare,” said study co-author Anny Xiang, a research scientist at Kaiser Permanente Southern California in Pasadena. The findings show that, although the risk of having a child with autism is still low among women who have gestational diabetes early in pregnancy (before 26 weeks), there is an increased risk compared to mothers without the condition.
The study, published today in the Journal of the American Medical Association, looked at more than 320,000 children born in Southern California between 1995 and 2009. About 8 percent of the kids were born to mothers who had pregnancy-related diabetes, and 2 percent had mothers with type 2 diabetes.
During an average follow-up period of 5.5 years, nearly 3,400 children in the study were diagnosed with an ASD, a group of developmental disabilities that can cause significant social, communication and behavioral challenges.
After the researchers accounted for other factors that can influence a child’s chances of developing autism — such as the mother’s age, education, income, ethnicity, prior pregnancies and the sex of the child (autism is five times more common in boys than in girls) — the impact of having gestational diabetes early in pregnancy was attenuated, but the link still held. Gestational diabetes by the 26th week of pregnancy was found to increase a child’s risk of autism by 42 percent compared with the risk of autism for children whose moms did not have gestational diabetes when these factors were considered.
Diabetes interferes with the body’s ability to move the sugar provided by food into cells. That can lead the levels of sugar in the blood to rise to unhealthy levels, damaging blood vessels.
While the exact reason for the link to autism is unclear, Xiang suggests that one underlying factor could be that the early months of pregnancy are a critical time period for brain development. If a developing fetus is exposed to elevated blood sugar levels during this important period of brain development, this may have some connection to the behavioral changes seen in autism after birth, she said.
Moreover, the study’s other findings hint that elevated blood sugar during early pregnancy, specifically, plays a role in the link. For example, the researchers found that children born to women who developed pregnancy-related diabetes after 26 weeks were not at greater risk of being diagnosed with autism than kids whose mothers never had type 2 or gestational diabetes.
In addition, the study found no increase in autism risk among the children born to women who knew they had type 2 diabetes before having a baby. This may be because these women are probably taking medication to control their blood sugar levels throughout pregnancy, Xiang said.
Because women who have no risk factors for diabetes may not be screened for the disease until the 24th to 28th weeks of pregnancy, gestational diabetes can go undetected during early pregnancy, she said.
Xiang cautioned that women who had gestational diabetes during pregnancy don’t need to panic or worry. The results suggest that for every 1,000 mothers who had pregnancy-related diabetes by 26 weeks, seven children may develop autism spectrum disorders, Xiang said.
Prenatal risk factors
While the exact causes of autism remain unclear, the new study adds to a growing body of research that suggests the brain changes related to autism occur long before delivery. Brain scans can now detect differences between autistic children and other kids when they’re only six months old.
Several studies have also found an increased risk of autism in the children of mothers who develop the flu or other infections during pregnancy, suggesting the condition may start to develop during the prenatal period. The link appears to be strongest for early-pregnancy infections, which is in line with the findings from the new study. Pregnant women also are more likely to have children with autism if they don’t get enough folic acid or iron, if they’re exposed to pollution, or if they take the anti-seizure drug valproic acid, research indicates.
Other studies have found an increased risk of autism in children who were born prematurely or very small, or who were born less than one year after an older sibling. Older mothers and older fathers are also at higher risk of having children with autism.
Genetics also appear to play a major role — in fact, one recent study found that nearly 60 percent of autism risk is genetic. Research also shows that about 15% to 20% of people with autism have a known genetic mutation that causes the condition. If one child in a family has autism, subsequent children have about a 1 in 5 to 1 in 6 chance of also having autism, studies show.
Based on the new findings, Xiang recommends that mothers-to-be should get their blood sugar checked early in pregnancy. Under current guidelines from the American College of Obstetricians and Gynecologists, women are routinely screened for gestational diabetes, but not until 24 to 28 weeks. A woman who has risk factors for gestational diabetes — such as being overweight, older than 25 or having a history of gestational diabetes — should consider earlier screening, such as at the first prenatal visit, Xiang said.
The researchers said early screening for autism in children born to mothers with gestational diabetes may also be warranted.