And the Mayer/Aniston baby rumors continue.

Jennifer Aniston is desperate become pregnant with twins before she celebrates her 40th birthday this February, Star Magazine reports.

“She knows her baby-making years are limited,” says a source. “It’s hard for her to think of anything else — she has babies on the brain!”

Jennifer has begun undergoing frequent holistic fertility treatments to increase her chances of conception.

“She’ll try anything to help her chances,” says a pal. “She and John are doing a lot of yoga together, and Jen makes sure to do specific poses her instructor suggested to help her get pregnant. Jen has also changed her diet. She’s taking a lot of folic acid and has upped her intake of milk and beef — all of which are supposed to increase your chances of having twins.”

“They can’t wait to be parents together,” the insider adds.