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updated 4/15/2015 2:15:56 PM ET 2015-04-15T18:15:56

Women who develop gestational diabetes early in their pregnancy have a higher chance of having a child with autism than women who don't develop the condition, a new study suggests.

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).

The finding does 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), the study did find a relationship between these women and an increased risk that the child would have autism, Xiang said. [ 7 Ways Pregnant Women Affect Babies ]

The study, published today (April 14) 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, including such conditions as autistic disorder and Asperger syndrome that can cause social, communication and behavioral problems in children. 

After the researchers considered 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 muted, 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.

Early exposure

The exact reason for the link is unclear. However, one underlying factor could be that the early months of pregnancy are a critical time period for brain development, Xiang told Live Science.

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 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.

© 2012 LiveScience.com. All rights reserved.

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