Dr Sheila Skeaff, who is leading the study, said it could lead to new recommendations on iodine intake for pregnant women.
She said 100 women in Hamilton and another 100 in Wellington had been recruited to take part in the study and she was now looking to recruit the same number of pregnant women in Dunedin.
The study comes after the Government decreed in 2009 iodised salt needed be added to all bread.
It was hoped this study would determine the ''right mix'' of diet and iodine supplements for pregnant women.
''What we need to see is that - given we started adding iodised salt to bread - if women do need to take iodine supplements [during pregnancy], how much do they need to take?''
At the moment, having the right diet and choosing what supplements to take could be confusing.
Getting enough iodine during pregnancy was important because it contributed to brain growth, she said.
Pregnant women from Dunedin who agreed to take part would be asked to attend a 15-minute appointment at the university.
Dr Skeaff said they were particularly interested in speaking to women in their first trimester. People interested in taking part were asked to call 0800 080 053.
