Researchers identified that children had a 63% greater risk of being diagnosed with autism if they had been exposed to gestational diabetes 26 weeks into the gestation period.
They found no significant association between an increased risk in autism and pre-existing type 2 diabetes in mothers, and there was no significant risk increase in mothers diagnosed with gestational diabetes after 26 weeks. Babies born to mothers with type 1 diabetes were not included in the study.
The US study, published in JAMA, analysed data from over 320,000 children of all ethnicities born between 1995 and 2009 in Southern California hospitals.
Child development disrupted
Within this dataset, 6,500 (2%) were exposed to pre-existing type 2 diabetes, while 25,000 (8%) were exposed to gestational diabetes. Following birth, around 3,400 children were diagnosed with autism.
The researchers said: ‘Our results help to clarify the relationship between exposure to maternal diabetes in utero and risk of autism spectrum disorders in offspring.
‘Because the association was stronger for gestational diabetes diagnosed at 26 weeks or earlier than for recognised pre-existing type 2 diabetes, we speculate that some children in [that group] may have been exposed to untreated hyperglycaemia during early critical brain developmental windows, which led to autism risk after birth.
‘Pre-existing type 2 diabetes may have been treated aggressively during pregnancy, which may have reduced the effect on foetal brain development.’
Negative health impact
They suggested that being exposed to hyperglycaemia during pregnancy could affect brain development in several ways, such as through hypoxia in the foetus, oxidative stress in cord blood or epigenetic factors.
Previous experiments have linked exposure to maternal hyperglycaemia to a series of long-lasting health effects on organ development and function in foetuses, including long-term obesity risk and metabolic disorders, but it has been less clear whether this could disrupt brain development.
The increased risk was independent of maternal smoking, pre-pregnancy BMI and gestational weight gain.
Trends suggest diagnoses of autism are on the rise, and the condition is estimated to affect almost 1.1% of the UK population.