Saldana, 36, is pregnant with her and husband Marco Perego's baby, reported Entertainment Tonight.
During an interview, when Spears was asked if she would do another film together with Saldana, the 'Hold It Against Me' singer replied, "Who knows? That's a very good idea. But Zoe's pregnant with twins right now. So I'm sure she's got a huge future ahead of her."
Britney, who already has two sons, then joked, "You're not ready. You don't know what you're in for."
Saldana confirmed her pregnancy while taking the Ice Bucket Challenge last month. At that time, the 'Guardians of the Galaxy' actress let her husband take the challenge.