The pregnant Meghan, Duchess of Sussex joined Prince Harry at a lunch reception in central Sydney after missing a cycling event earlier in the day on Sunday.
Harry told some Invictus competitors his wife was "resting back at home, pregnancy takes its toll", according to the MailOnline.
The Sussexes are currently part-way through a gruelling 16-day tour of Australia, New Zealand, Fiji and Tonga, with 76 events on their schedule.
The mother-to-be opted to rest following a late night on the forecourt of the Sydney Opera House, after an electrical storm delayed the launch event of the Games.
A source said: “She is not sick, just tired.”
At the reception, where they met Invictus competitors and other guests in a crowded restaurant, the duchess appeared lively and engaged.
The source said that they had expected to return to Admiralty House, where the couple is staying, by 9pm last night. However because the opening was delayed by a thunderstorm, they did not get back until around 10.45am.
“We have to try to pace her. We have to make sure she is well paced and not overdoing it.
“She had a very late night last night.
“She wants to do everything, but Prince Harry is encouraging her to pace herself.
“We want to make sure she gets enough rest at the beginning of the day and at the end of the day.
“If it has been a very late night due to unforeseen circumstances, we have to adjust for that.”
Kensington Palace confirmed that Meghan, 37 - and believed to be around 12 weeks pregnant - will limit her schedule after consulting her husband, Prince Harry.
The announcement that the royal couple were expecting a their first child was revealed at the start of the four country tour.
A statement by the palace today said, “After a busy programme, The Duke and Duchess have decided to cut back The Duchess's schedule slightly for the next couple of days, ahead of the final week and a half of the tour.
“The Duke will attend the cycling as scheduled this morning, and The Duchess will join him for this afternoon's engagements. The Duke will continue with the engagements on Fraser Island as planned,” the statement said.
The couple fly to Fraser Island today in Queensland before heading to Fiji, Tonga back to Sydney and finally New Zealand.
“She’s feeling fine, but resting,” said a source.
Sources say Meghan isn’t feeling sick but the palace are trying to pace her given how many engagements are coming up.
The royal couple are due to undertake 76 engagements in all on the 16 days tour.
It is unlikely Meghan will do many of the the engagements on Fraser Island due to the terrain.
At Sunday's Invictus event, Prince Harry was given a pair of budgie smugglers - and promptly put them on over his jeans.
They were presented to the Duke of Sussex when a disabled sports presenter and two members of the Australian Invictus Games team visited him at Admiralty House, the Governor General’s residence where the couple are staying in Sydney.
Dylan Alcott, a host on ABC’s daily round-up of the games, had a private talk with Harry along with team members Matt Model and co-captain Nicole Bradley.
Mr Alcott, who is a triple Paralympic gold medallist in wheelchair tennis and wheelchair basketball, said: “We gave him a gift. One of the athletes, Matt, gave him a pair of budgie smugglers. And he put them on, over his jeans. It looks awesome.
“He said, ‘Shall I put them on?’ We said, ‘One hundred per cent.’ So he put them on… Good on him.”
Mr Alcott, who was talking at a reception hosted by the prime minister Scott Morrison at a restaurant in Sydney’s Botanical Gardens, added: “I just met the duchess, and he [Harry] said he [Dylan] is the one to blame for the photo. I said, ‘Hey, sorry!’”
Talking about the budgie smugglers, he added: “I think it did wonders for him. It looked good. He should make it official! I reckon the duchess will love them. But who knows? Maybe not.”
He went on: “I met the duchess before, at Wimbledon - I’m the number one wheelchair tennis player in the world. I said, ‘We actually met at Wimbledon.’ She said ‘I remember meeting you at Wimbledon.’ I was pretty happy with that. I felt pretty chuffed that she remembered.”
He added: “To sit on the lawn, and just have a chat with him about some really important issues, like mainstreaming disability, talking PTSD - what he has done is normalised it a lot, so people feel comfortable. As someone who has had a disability my whole life, it really meant a lot to me to be able to say thank you. He is such a good bloke.”
Meghan joined Harry for later engagements on Sunday, with the couple attending a reception at the Pavilion Restaurant in the Domain for Invictus competitors, their families and friends hosted by Australian Prime Minister Scott Morrison.
At the reception the couple met children from Kookaburra Kids, an organisation which helps children living in families affected by mental health issues.
Lachlan Williams, 10, from Sydney, said: “He asked which of our parents were in the military, and we put up our hands to say yes.
“Afterwards I said to them, ‘My teacher says she loves you.’ They laughed.”
The couple had a busy Saturday, starting off with the opening of an extension to the Anzac memorial in Hyde Park, then on to Cockatoo Island to watch the Jaguar Land Rover Driving Challenge as part of Invictus.
In the evening, the couple attended a reception for the Games and went on to attend the opening ceremony.
They will next travel to Fraser Island, off the coast of Queensland, with Monday's planned engagements including a visit to Lake McKenzie and a walkabout on the Kingfisher Bay.