The World Health Organisation says new research has strengthened the link between the Zika virus and foetal abnormalities, while sexual transmission of the virus is more common than previously thought.
This year, Zika has been detected in five Pacific Island countries.
A meeting of the WHO's Zika Emergency Committee in Geneva concluded that the Zika virus does affect the brain of a developing foetus and can also cause neurological disorders.
The WHO is advising pregnant women who have sexual partners who live in or travel to areas with Zika outbreaks to either practise safe sex or abstain from sex for the duration of their pregnancy.
They are also advising pregnant women not to travel to areas of ongoing Zika virus outbreaks.
Transmission of the virus has now been reported in 31 countries and territories worldwide, with five of those located in the Pacific.
They are American Samoa, Samoa and Tonga, while Fiji and New Caledonia reported their first Zika cases this past week.
The New Zealand government is advising anyone travelling to any Pacific Island countries to take precautions to avoid mosquito bites.