Women who are obese or have diabetes while they are pregnant may be more likely to have a child with autism or developmental delays, a new study reports.

Though the study does not show them to be a cause of children's developmental difficulties, it is the first time a strong association has been found between maternal obesity and diabetes and children's autism or learning and language problems, researchers say.

Researchers found that obese expectant mothers were 1.6 times more likely to have a son or daughter with autism, and were more than twice as likely to have a child with another developmental difficulty.

Women with diabetes — either type 2 diabetes or pregnancy-related diabetes — had 2.3 times the chance of having a child with language and learning delays, according to the findings.

“This is one of the earliest studies to look at the prenatal environment, at a more detailed level, to see whether it was a factor behind the rising rates of autism,” said lead author Paula Krakowiak, a doctoral candidate in epidemiology at the University of California, Davis.

Further work is needed to confirm the results, the researchers said. Their study appears online today (Apr. 9) in the journal Pediatrics.

Prenatal influences

In the study, researchers looked at 1,004 boys and girls between the ages of 2 and 5 and their mothers, all of whom gave birth to them in California. Among these children, 517 were diagnosed with an autism spectrum disorder, and 172 kids had a developmental delay. There was also a comparison group of 315 children whose development was normal.

All the youngsters were participating in a long-term study of how genetics and environmental factors influence a child's risk of autism.

During this research, scientists also looked at a possible connection between children's neurological development and mothers who had high blood pressure when they were pregnant, but the number of women with hypertension was too small to produce firm conclusions, Krokowiak said.

“The study highlights — if not for a mother's own well-being, then for the well-being of her baby — [her need] to make any lifestyle changes she can to reduce her risk of obesity and diabetes during pregnancy,” Krokowiak said.

Early brain development

As for why maternal obesity and diabetes may be linked with autism in children, researchers proposed a few mechanisms.

One possibility, Krokowiak explained, is that when a mother's blood sugar levels are high, more glucose crosses the placenta. This causes the fetus to produce higher levels of insulin and causes it to grow faster, use up more oxygen, and possibly not get enough oxygen from maternal blood supplies to meet the needs of its developing brain.

A second explanation for the link is that being obese or having diabetes during pregnancy results in the mother developing increased resistance to insulin and higher levels of chronic inflammation. When more proteins linked with inflammation cross the placenta, the baby's normal brain development may be disrupted.

Although this research looked at how prenatal factors may be linked with autism, scientists suspect that both genetic susceptibility and environmental factors occurring before or during birth play roles in early brain development.

“This study does not prove that having a metabolic condition in pregnancy, such as type 2 diabetes or gestational diabetes, causes autism or other neurodevelopmental problems in the offspring,” said Linda Dodds, a professor in the departments of obstetrics & gynecology and pediatrics at Dalhousie University in Nova Scotia, who was not involved in the research.

Still, Dodds and her colleagues recently published a study that also linked maternal obesity with an increased risk of autism in children.

“The findings of this study and the proposed mechanisms are interesting,” Dodds said. Yet how exactly how the link might work, and whether changes in a mother's lifestyle before or during pregnancy could actually reduce the risk of autism, remain unclear.

Dodds said, “As is common in many research studies, the results tend to raise more questions than it answers.”

Pass it on: A strong link is found between obesity or diabetes during pregnancy and an increased risk of  developmental difficulties, including autism, in the child.

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