Mums-to-be who smoke marijuana are five times more likely to give birth prematurely, new research reveals.
The University of Adelaide-led study looked at more than 5500 women from Australia, New Zealand, the UK and Ireland and the effects of using the drug throughout the first 20 weeks of pregnancy.
It's the first time that ongoing marijuana use during pregnancy has been directly linked to premature or pre-term birth.
More than 5.5 per cent of expecting mothers reported consuming it during or before pregnancy, making it a "major public health concern" for them and their babies, University of Adelaide lead author Claire Roberts says.
She also says more than six per cent of premature births could have been prevented if expecting mothers had abstained.
In Australia, which had the highest proportion of pregnant marijuana users, this figure jumped to almost 12 per cent.
"Anecdotally, we know that some women are using marijuana to reduce nausea in pregnancy even though there is no medical evidence to support this," Prof Roberts said.
"Our study was unable to determine whether there is a `safe' time prior to 20 weeks' gestation to give up marijuana. Therefore, we recommend total abstinence."
