While many celebrities like Kristin Cavallari, Hilary Duff, Jennifer Garner, and Alyson Hannigan are openly celebrating their pregnancies, some stars bellies are only rumored to be growing. 

Angelina Jolie, Snooki, Jennifer Aniston, Rosie O'Donnell and Catherine Zeta Jones are all celebrities whose pregnancy is purely speculation. So let's break down the invisible baby bump.

Angelina Jolie and Brad Pitt, who already have six children, are supposedly expecting twin boys. This unexpected news has also caused them to reconsider getting married.

OK! Magazine spoke to a source who said, They were overjoyed at how quickly Angie became pregnant this time. They said that it showed that this pregnancy was 'meant to be.' But then Angie's latest ultrasound revealed there were two heartbeats - well they couldn't believe it. They were totally shocked!

Then there is the pint-sized guidette Snooki and boyfriend Jionni. The couple has had their ups and downs. Now it is being rumored that the two, whose big fight in Italy got broadcast on Jersey Shore, are bringing a baby fist pumper into the world.

Jionni is a great guy so I'm so down for making Guido babies with him, Snooki had said last summer. Sources are reporting that Snooki is overjoyed with news of a baby with Jionni, and that MTV is working on incorporating the pregnancy in the Snooki/J-WOWWW Jersey Shore spin-off.

If all the Jennifer Aniston pregnancy rumors were true, the Wanderlust actress would have been pregnant for years. Aniston and beau Justin Theroux met on the set of Wanderlust, and it has been reported that Aniston has requested to take some time off from acting. What does 'time off for acting' mean in the gossip world? That the 42 year old is pregnant.

Rosie O'Donnell might have only recently gotten engaged to girlfriend Michelle Rounds, but reportedly the two are anxious to get pregnant. O'Donnell admitted on her OWN talk show that she and Rounds are starting the family planning process. According to a source that talked to Us Magazine.

Michelle is seeing a fertility doctor. She is really excited and they cannot wait to add to their family. Rosie goes to all of her doctors' appointments with her and is really supportive. She isn't pregnant yet but they hope as soon as possible she will be.

Michael is giving Catherine her dream gift - another baby, said a Star Magazine insider on Catherine Zeta Jones and Michael Douglas.  A fuller figure and her absence from Sundance was reportedly a sign of her pregnancy.  A rep for Douglas has since told GossipCop.com that the pregnancy is not true.

Only time will tell if these stars are bringing new life into the world. Until then we can look for clues hidden in baggy shirts and well placed bags.