As Katie Holmes stepped out of the car and walked into Victoria Beckham's 34th birthday party she must have known she'd make headlines around the world. Clad in a shapely golden yellow dress, there was no mistaking a small but undoubtedly defined 'baby bump'.

Tom Cruise, 45, and his wife Katie have been trying to have another child for months, but in recent times their efforts have been sidetracked by a series of bitter arguments.

With 29-year-old Katie planning a make-or-break trial separation, the news couldn't have come at a more complicated moment.

One of Katie's close pals spoke exclusively to New Idea, saying: 'It's unbelievable! Tom and Katie talked about having another baby late last year and they've done everything to get pregnant ever since.

'They didn't have any problems conceiving Suri, but it just didn't seem to be happening this time around. Then they had a really rocky few months, and to be honest, getting pregnant was the last thing on their minds. Now it's as if, as soon as they stopped trying, along comes a stork.'

The big question now is how will Tom and Katie react to their extraordinary news?

According to numerous sources close to the couple, the pressure surrounding their attempts to have another baby may have actually been an underlying cause of a lot of tension between them.

Another friend explains: 'They both thought it'd be so easy. Once they made the decision to start trying again, they expected it to take a few weeks like it did the first time.

'But then constantly taking pregnancy tests and studying Katie's fertility chart really led to a lot of frustration and stress.

'There were obviously different triggers to every row but trying to get pregnant was always the "elephant in the room".'

But now with the 'elephant' gone, Tom and Katie seem likely to put their problems behind them and concentrate on looking forward to the blessing of another child.

One family member who'll undoubtedly be thrilled with the news is their daughter Suri. The toddler was treated to a fun-filled second birthday party just over a week ago, but when Tom and Katie told her she could have anything she wanted, she told them: 'I want another brother.'

Suri has forged a close attachment to Tom's adopted children Isabella, 15, and Conor, 13, and Tom admits: 'Conor's often the one who gives her the first bottle of the day.'

Now it seems Suri will get her wish for a baby sibling, and Conor and Isabella will have another baby to help look after.

Shortly after Suri's birth, Katie spoke about the siblings' bond.

'It's really special to see Bella and Conor holding their little sister and to hear them talk about all of the fun things they're going to do together.'

And now there'll be a sixth member of the Cruise family for all future adventures.

For the meantime, very few people know the news. But by the way Victoria hugged and kissed Katie and stroked her tummy throughout the party, Posh is in the know.

Many of the other guests might have noticed Katie and Eva Longoria Parker were the only two party-goers who passed on the high-priced wine and champagne.

With rumours flying the Desperate Housewives star is pregnant, neither Eva nor Katie did much to dampen speculation - although both their publicists have denied there are babies on the way.

Katie also seemed to be being congratulated by a number of high-profile Scientologists at Suri's birthday party two days earlier.

The party, at a private estate in the Hollywood Hills, was crammed with members of the controversial religion. No doubt they're in the loop as Scientology insists its members confess all their secrets.

In any case, just over 48 hours later, Katie's bulging party dress meant there wasn't much of a secret left to keep.