Gwyneth Paltrow had to reveal her pregnancy to the world, because it's obvious she is expecting in new movie PROOF.

The actress kept her status a secret for months, but concedes fans would have found out when they saw the film - which she shot during the early stages of pregnancy.

She says, "My boobs are much bigger in the movie than they are normally. That's a tell-tale sign."

Paltrow adds it was tough making a film while going through morning sickness: "The beginning of a pregnancy can be very difficult - nauseating and then exhausting."