Obese women and those with Type 2 diabetes could be increasing their chances of having a child with autism or another development disorder.
A U.S. study says that high glucose levels during pregnancy could affect brain development in the foetus.
The Paediatrics study by the University of California that looked at 1,000 children and mothers over seven years.
In California, where the study was carried out, 1.3 per cent of women have Type 2 diabetes and 7.4 per cent have diabetes which developed during pregnancy.
The children in the study were aged between two and five years old and were enrolled between 2003 and 2010.
Among children whose mothers had Type 2 diabetes during their pregnancies, the study found that 9.3 per cent of those children had autism.
And 11.6 per cent of that group of children showed evidence of a developmental disability. This was nearly twice as high as the 6.4 per cent of children with these problems born to women with no metabolic conditions.
Over 20 per cent of the mothers of children with autism or other developmental disability were obese, compared with 14 per cent of the mothers of normally developing children.
Dr Matthew Hobbs, head of research at Diabetes UK, told the BBC that more research was needed to answer questions not investigated in the study.
"It is important to note that while it does show an association, it does not show that diabetes causes developmental problems," he said.
"We continue to advise that women with diabetes should tell their diabetes health care team if they are planning to become pregnant. They can then work together to make sure they are aware of the steps they should take to help them have a healthy pregnancy."
Obese Mothers Increase Risk Of Having Autistic Children, Says Study