Ron Howard's actress daughter, 25, wed long-term love Seth Gabel in June and recently revealed she had changed from vegan to vegetarian so she could boost her amino acid levels.
The glowing star announced her happy news at the British premiere of her latest film Lady in the Water in London last night.
She enthused, "I can't talk about the pregnancy too much. I'm a little superstitious."
Her co-star Paul Giamatti joked, "I had nothing to do with it!"
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