The 27-year-old - who was signed on for the 2020 Suncorp Super Netball season - featured as a replacement player in the NSW Swifts' 2019 Premiership-winning campaign, joining the team for Rounds 11 and 12 and making her debut against the West Coast Fever in Perth.
Johnson, who has 47 New Zealand caps, has been playing elite netball since 2010 having previously represented the Northern Mystics in the trans-Tasman ANZ Championship and, more recently, the Northern Stars in New Zealand's ANZ Premiership.
She won a silver medal with the Silver Ferns at the 2015 Netball World Cup in Sydney, and gold in two Fast5 World Series, before making the move to Australia last year to be with partner Shaun Johnson, who plays in the NRL for the Cronulla Sharks.
The couple were married in December and will welcome their first child later this year.
NSW Swifts Head Coach Briony Akle said everyone at the club was delighted for the Johnsons as they prepare for the new arrival.
"First up, I would like to congratulate Kayla and Shaun on this joyous news, which is a real blessing," she said.
"Obviously I would have loved to see more of Kayla in the Swifts dress but if we were to lose her for any reason, I'm glad it is this.
"Kayla came in last year against the Fever in Perth and showed her class in what was a very important away win for us on our way to the title.
"I know she was very excited about testing herself further in the Super Netball environment, but sometimes life happens and now she is about to embark on a different, but very special, journey.
"I have four boys myself and I know the upcoming months will be very busy and exciting for Kayla.
"All of our players and club staff would like to wish her and Shaun the very best for the coming months and we hope to see them in the stands for a game at some stage with the bub."
Johnson's replacement in the NSW Swifts squad will be determined in the coming weeks.
