Health experts are warning Australians to be cautious about the growing number of prenatal supplements being promoted to expectant parents, particularly through social media influencers.

Australian pregnancy guidelines recommend folic acid, iodine and iron for most pregnant people.

However, experts say many additional supplements being marketed online have little evidence of benefit and, in some cases, could potentially cause harm.

They are urging expectant parents to speak with their doctor, midwife or pharmacist before taking supplements, rather than relying on social media recommendations.