Women considering pregnancy, who are pregnant, or are breastfeeding are recommended to take an iodine supplement each day containing 150mcg of this trace mineral.

Lead researcher Andrew Reynolds, says he and colleagues asked women from all over the country to tell them what supplements they were taking, and when.

The new study appearing in the Australian and New Zealand Journal of Obstetrics and Gynaecology.

Research has shown iodine is important for optimal foetal and infant brain development, including their IQ later in life.