New research has found that some pregnant women should be taking four times the level of vitamin D currently recommended in New Zealand.
The University of Auckland study was done in collaboration with Harvard University in the United States. Its aim was to find out how much of the vitamin is needed to ensure that newborn babies are not deficient.
The study's lead author, Associated Professor Cameron Grant of Auckland University, says current recommendations vary widely between Australia, North America, Europe and New Zealand.
Pregnant women were split into three groups with different dosage strengths and the higher the dosage, the longer normal levels of vitamin D stayed in the body.
The study's findings have been published in the American journal Pediatrics.
Dr Grant told Radio New Zealand's Checkpoint programme on Tuesday that supplements should be recommended. However, he says one dosage won't fit all and factors such as ethnicity will need to be taken into account.
"What I don't think is that one size will suit all. We're going to need to understand a little bit more about how much should be recommended for a woman based, for example, on her ethnicity and on the season of the year that she finds herself in."