"Avatar" actress Zoe Saldana has for the first time acknowledged that she is pregnant via a video of her ALS Ice Bucket Challenge, an activity where people dump a bucket of ice water on one's head.

While Saldana couldn't take the Challenge herself due to her pregnancy, she got her husband, Marco Perego, to complete it on her behalf, reports femalefirst.co.uk.

Perego took her place to complete the task by having freezing water poured over his head to raise awareness for the nerve cells disease.

Turning to the side and rubbing her growing baby bump, the 36-year-old actress, who was nominated by director James Gunn, said in the video: "I am accepting James Gunn's challenge to take on the ice bucket challenge.

"Obviously, I can't do it myself so I nominate my husband to take on the challenge and get rinsed with a nice bucket of ice water."

Saldana later nominated four people, including James Cameron and Salma Hayek, to take on the challenge next.

She has been tight-lipped about her pregnancy until now and a source had previously said: "She will only announce the news when she's ready."