Britney Spears reveals Zoe Saldana is expecting twins! Credit: Mark Davis/Getty Images;Dave J Hogan/Getty Images

Whoops! Britney Spears let it slip during an interview with Entertainment Tonight on Tuesday, Sept. 9, that her Crossroads costar Zoe Saldana is pregnant with twins.

Asked whether she and Saldana would do another movie together, the singer replied, "Who knows? That’s a very good idea. But she’s pregnant with twins right now. So I'm sure she's got a huge future ahead of her."

After confirming that the expecting Avatar actress will have her hands full, Spears went on to say of motherhood, "You're not ready. You don't know what you're in for." (The mom of two's insight comes just a day after she reunited with Saldana at LAX.)

The Guardians of the Galaxy star has been less vocal about her pregnancy, only just confirming she's expecting during her ALS Ice Bucket Challenge video last month.

In the adorable clip, the 36-year-old opted out of the challenge, rubbing her belly and telling the camera: "Obviously, I can't do it myself so I nominate my husband [Marco Perego] to take on the challenge."