The 'Thank You For Smoking' actress - who has three-year-old daughter Suri with husband Tom Cruise - is said to have spent four hours at the Hollywood Scientology Center last week, sparking rumours she is getting ready to expand her family.

A source told the New York Post newspaper: "This is exactly what happened just before she got pregnant with Suri. Tom has made no secret of the fact that he would like another baby."

According to a website run by the Church of Scientology, followers believe the "health and the sanity of the child begin long before birth".

Scientology auditing is used to restore self confidence, happiness and spiritual freedom and involves answering questions or following directions with the aim of being freed from unwanted barriers that inhibit natural ability.

This is not the first time Katie has undergone special treatment at a Scientology centre.

Last year, she reportedly underwent a 'Scientology Sparkle' makeover.

A source said at the time: "The makeover was Tom and Church of Scientology leader David Miscavige's idea. After Katie followed the Purification Rundown - an extreme detox where she had high doses of vitamins and spent five hours a day in a sauna - doctors and homeopaths were called in to maintain her looks and ensure her skin would not break out, a process dubbed the 'Scientology Sparkle'."

As part of her makeover, Katie enjoyed two days of pampering at the Tokyo Ritz Carlton spa, including hot volcanic stone massages, a rejuvenating facial and manicures and pedicures.

Katie Holmes is reportedly undergoing Scientology 'auditing' in preparation to have another baby.