A new study now shows that women with any form of diabetes are at greater risk of having children with an autism spectrum disorder.
The study found it included women who did not have diabetes before they got pregnant but developed it while carrying their babies, as well as those who had type 1 diabetes throughout their lives.
Research, in recent years, has pointed toward a link between the condition, the immune system and the developing foetal brain.
Research from the Kaiser Permanente health system in California suggests that the inflammation, toxic levels of glucose and immune system effects of all kinds of maternal diabetes may increase the child's risk of autism by as much as two-fold.
Studies have identified more than 100 genetic links or mutations that seem to increase an individual's risks of autism, but 85 per cent of cases are not explained by these DNA factors.
According to researchers environmental factors interact with these genes and lead to changes that affect the earliest stages of a baby's brain development.
Researchers are most interested in how oxygen deprivation (for the baby), viruses and diabetes during pregnancy might affect autism risks for a woman's child.
Two years back, lead study author Dr Anny Xian and her team at Kaiser Permanente found that women who were diagnosed with gestational diabetes before they had been pregnant for 26 weeks were at a 42 per cent greater risk of having a child with autism than other women were.
They did not find the same risks associated with gestational diabetes diagnosed later on in the pregnancy, but in the new research, Dr Xian's team discovered that any earlier development of diabetes in the mother seemed to raise risks for autism.