Transcript for Meghan Markle, Prince Harry to welcome baby in the spring

Finally tonight, Harry and Meghan, and the royal secret no longer. James Longman, with the Royals in Australia. Reporter: Just hours after Meghan and Harry touched down in Australia, news of a royal baby rocketed around the globe. That's fabulous. We were very pleased. We knew it was coming soon. Reporter: Kensington palace announcing the duke and duchess will welcome a baby this spring. Pregnancy rumors had swirled for weeks. And fueled by Meghan wearing an overcoat to princess Eugenie's wedding. And it was on that day that Harry and Meghan shared their news with family and friends. The couple, asked about children during their engagement interview with the bbc. One step at a time. And hopefully, we'll start a family in the near future. Reporter: Five months after that fairytale wedding, they're on their way. Meghan is about 12 weeks along. A first grandchild for Meghan's mother. And an eighth great-grandchild for the queen. Both, said to be delighted. The news of another royal baby who'll be seventh in line to the throne has electrified an already high-profile trip to Australia. It's a sentimental journey made by Diana and William. Years later, a visit with prince George. Tonight, Harry and Meghan are making their own special memories down under. James Longman, ABC news, Sydney. Thanks, James. I'm David Muir. I hope to see you right back here tomorrow. Until then, have a good evening.

This transcript has been automatically generated and may not be 100% accurate.