Expectant mums face no shortage of advice on what they should and shouldn't eat but the latest research says excluding two foods during pregnancy could do more harm than good.

Mums who do not eat cooked fish or eggs have a higher risk of having kids with childhood obesity, a University of Southern Queensland study shows.

Data collected from more than 10,000 children over 15 years was analysed by lead author Brenton Horne to see what causes high rates of childhood obesity.

The information includes whether their mothers ate fish, eggs, meat, dairy and other foods during pregnancy.

"One possible risk factor I hypothesised was mothers excluding particular food items from their diet," he told AAP.

"When I checked for an effect I found only fish and eggs were associated with an elevated risk for childhood obesity and/or overweight."

Mr Horne found excluding fish had a particular impact on kids aged 6-7 while cutting out eggs affected those 14-15.

Removing meat from the equation made little difference.

So what is it about fish and eggs?

Mr Horne said it might be the omega-3s present in both foods that notably prevent obesity in kids, although some meats have similar levels of fatty acids.

It suggests there is something more to fish and eggs which requires further research.

"Our study only looked at whether exclusion of these food items has an effect," Mr Horne said.

"It did not look into how often and much mothers that didn't exclude these foods actually ate them and hence cannot tell us the optimum frequency and quantity of these foods in expectant mothers' diets."

The study also did not establish causality.

Mr Horne hopes further research will lead to changes to dietary advice and ideally fewer cases of childhood obesity.

For mums-to-be who do not want to eat fish or eggs and instead take supplements including iron and folate, the research revealed the vitamins did not protect against the childhood obesity risk.

Mr Horne said expecting mums should avoid relying on vitamins for these nutrients.

Fish, meat, eggs and dairy remain key for a pregnant woman's diet.

But Mr Horne says research shows excluding other food types may also reduce risk.

"It is important, as childhood obesity and overweight is an ever increasing issue in modern times," he said.

Notably, it can boost the likelihood of cardiovascular disease, type two diabetes and cancer into adulthood.

Although his research raised questions, Mr Horne said pregnant women should continue to follow the Australian dietary guidelines.

His research was published in the PLOS ONE journal.