"Harry and Meghan have taken medical advice from doctors back in the United Kingdom about the risk of Zika in Fiji and Tonga, and they have decided on that medical advice that they will carry on, and nothing will change", Nikkhah told CBS News.
They will spend the next 16 days in Australia, Fiji, New Zealand and Tonga as part of their first official tour as a married couple.
Hundreds of well-wishers gathered with umbrellas outside the airport and Admiralty House in the hope of catching a glimpse of Harry and Meghan.
Meghan arrived with Prince Harry at St George's Chapel in the grounds of Windsor Castle; keeping a very low profile last week, and wearing a navy blue dress by Givenchy (which just so happened to be the designer of her wedding dress).More news: Cologne station shut down in 'hostage situation'
Kensington Palace tweeted on Monday morning that the pair were "very pleased to announce" the Duchess of Sussex is expecting.
Tonight the Royal couple will attend a reception at Admiralty House where they will meet charity and business leaders.
There are parallels between her life and that of Princess Grace, another American who left a successful Hollywood career to marry Prince Rainier of Monaco and start a royal family.
Tuesday is the first opportunity for the public to interact with the couple - and to be the first to congratulate the royal couple. For those wondering if they are continuing their 16-day trip, which includes plans to visit countries with moderate Zika risk, the answer is yes.
Everyone's feeling the love for the latest royal baby.More news: Customers asked to limit use of natural gas | Cranbrook, East Kootenay
They also accepted good wishes from dignitaries including the Premier of New South Wales, the Hon Gladys Berejiklan MP.
It's believed that Meghan is around 12 weeks pregnant.
The news of a Royal baby surprised many, including Governor-General Sir Peter Cosgrove and Lady Cosgrove, who dispatched a staff member to hastily purchase a toy kangaroo with joey for their pregnant guest.
Regardless of gender or sex, Baby Sussex will supersede Prince Andrew in the royal line of succession and will also be seventh in line to the throne. Meghan and Harry just kicked off a royal tour of Australia on October 14, so we'll get plenty of look at Meghan's maternity style over the next few weeks.More news: Trump, Xi to meet amid trade war tensions