Caitlan Johnston-Green's pregnancy could rule her out of her first season with Cronulla.

The NSW State of Origin representative, widely regarded one of the NRLW's best props, announced on Instagram she and her partner were expecting their first child in May next year.

That same month, clubs will return to training ahead of the new campaign that begins on July 3, with 2024 runners-up the Sharks hosting Parramatta in the first game of the year.

Dual premiership-winner Johnston-Green had been tipped as a major acquisition for Cronulla, who have lost middle forwards Holli Wheeler and Teagan Dymock to expansion side Canterbury for the 2025 season.

But Johnston-Green's availability is now under a cloud, and subject to consultations with medical staff at the former Newcastle Knight's new club.

The Sharks are yet to determine whether they will sign a player to replace 23-year-old Johnston-Green in their top 24 squad.

"As a club, we're thrilled for Caitlan and will support her in every way she needs throughout this journey," the Sharks said in a statement to AAP.

"Our medical team will work with Caitlan and ensure she receives the best care and guidance ahead of a return to the field when the time is right for her."

Sam Bremner, Tazmin Rapana and Corban Baxter are among NRLW players to have returned to the field after pregnancy.

Johnston-Green will remain with Cronulla until the end of the 2027 season, having signed a three-year deal prior to an injury-affected 2024 campaign.