While the country's Ministry of Health (MOH) does not usually recommend supplement intake, it encourages mothers to consume additional folic acid and iodine before and during pregnancy, and iodine when breastfeeding.
The purpose of doing so is to minimise the risk of neurodevelopmental problems in infants.
The MOH recommends that women who want to have children, are pregnant, or are breastfeeding should take 150mcg of iodine supplementation a day, as it is vital to maximising foetal and infant brain development.
The ministry also recommends that expectant mothers take one 0.8mg folic acid tablet daily from four weeks prior to conception to 12 weeks after conception, in order to help prevent neural tube defects in the infants.
The university conducted a first-of-its-kind study to determine how many mothers actually heeded the MOH's advice, and found that just slightly over a third of the mothers they surveyed adhered completely to the recommendations.
The study's lead author, Dr Andrew Reynolds, a research fellow at the university's Department of Human Nutrition, told New Zealand media, "We heard from 535 women who were pregnant, or had been pregnant in the last two years.
"The responses revealed only 52% of these women were following the iodine recommendation, and only 38% of them followed both the iodine and the folic acid recommendation."
Education and promotion needed
The study’s co-author, Assoc. Prof. Sheila Skeaff, added that "although these data are from a survey that captures supplement use at one time point, we found the results very interesting".
Of the surveyed women who were consuming iodine, 80% were obtaining it using a midwife's or GP's prescription, which the MOH subsidises.
Still, the survey results are seen as a cause for concern.
Skeaff said: "We need to make a bigger effort to promote these recommendations and increase access to iodine and folic acid supplements — we want communities to know about these nutrients, and why they are important."