Australian researchers have found pregnant women with low vitamin D levels at 20 weeks' gestation are more likely to have a child with autistic traits.

The important role vitamin D plays in early human life is back in the spotlight after Australian researchers noticed a link between a deficiency in pregnancy and autism.

The research, led by The University of Queensland's Brain Institute Professor John McGrath and involving Dr Henning Tiemeier from the Erasmus Medical Centre in The Netherlands, found pregnant women with low vitamin D levels at 20 weeks' gestation were more likely to have a child with autistic traits by the age of six.

"This study provides further evidence that low vitamin D is associated with neurodevelopmental disorders," Professor McGrath said on Wednesday.

The finding has led to calls for the widespread use of vitamin D supplements during pregnancy, just as taking folate has reduced the incidence of spina bifida in the community.

Prof McGrath says supplements may reduce the incidence of autism - a lifelong developmental disorder that greatly inhibits a person's ability to communicate.

"We would not recommend more sun exposure, because of the increased risk of skin cancer in countries like Australia," he said.

"Instead, it's feasible that a safe, inexpensive, and publicly accessible vitamin D supplement in at-risk groups may reduce the prevalence of this risk factor."

Vitamin D usually comes from exposure to the sun, but it can also be found in some foods and supplements.

While it's widely known vitamin D is vital for maintaining healthy bones, there's also a solid body of evidence linking it to brain growth.

The study examined approximately 4200 blood samples from pregnant women and their children, who were closely monitored as part of the long-term "Generation R" study in Rotterdam, The Netherlands.

Blood samples with a vitamin D reading of less than 25.0 nmols is considered deficient.

Autism and child development expert Professor Andrew Whitehouse from the Telethon Kids Intstitute is an advocate for the use of the essential vitamin during pregnancy and says the results of this study are not totally surprising and potentially very important.

But they are not conclusive and need to be put into perspective.

"There are likely dozens, if not hundreds, of different mechanisms that can lead to autism. Now this study gives us an inkling of one possible mechanism but before we think about anything we need to see a replication of this finding."

Vitamin D deficiency during pregnancy has previously been linked to many different conditions including schizophrenia, asthma and reduced bone density.

"What we know is that vitamin D during pregnancy is very important for how the baby develops," said Prof Whitehouse.

Earlier this year, an Australian study, published in the Journal of Allergy and Clinical Immunology, showed vitamin D wasn't just important during pregnancy but also in the first decade of a child's life.

Researchers at the Murdoch Children's Institute found evidence of a clear link between a lack of vitamin D in early childhood and allergic disorders such as asthma and eczema.