Kim Kardashian is worried Kris Humphries will try to ruin her baby joy.

The 'Keeping Up With The Kardashians' star is expecting her first child with boyfriend Kanye West but after discovering her estranged husband Kris Humphries could legally claim custody, Kim is upset her marriage is casting a shadow over this happy time.

A source close to Kim told HollywoodLife.com, ''Kim was shocked when she found out that Kris could technically try to get custody. It sounds totally crazy! Why would he do that when it's only going to make him look bad. But Kim wouldn't put anything past Kris, all he cares about is hurting her, so of course she's worried that he'll do something to ruin the best moment of her life.''

Kim is in the middle of divorcing Kris and wants to remove him completely from her life, so that she can focus on moving on with Kanye and their baby.

The insider added: ''It's upsetting for her, but she's still not going to give in. Kim's a fighter and even though a lot of people think that Kim took advantage of Kris it was the other way around. She did love him and she gave him 100 per cent so there's no way she's going to turn around and say it was a fraud - that would be lying to the court.''