Holly Madison has been in the number one girlfriend spot for years now with Playboy mogul Hugh Hefner. While she plays nice with the other two girlfriends, Bridget Marquardt and Kendra Wilkinson on their E! series The Girls Next Door, one gets the clear message that Holly is hoping for some solid one-on-one relationship time with Hef at some point.

She's also never made it a secret that she would love a little Hef of her own. We learned in 2007 that she and Hef were putting away a little something for a rainy day: Hef's sperm. Now is it possible that the rainy day is here and Holly and Hef are going to be bringing a new addition to The Girls Next Door house?

It's been rumored that Holly and Hef were at a fertility clinic recently. Janet Charlton's Hollywood column says, "Holly and Hef were seen in the waiting room of a Beverly Hills gynecologist who specializes in in vitro fertilization. Other couples trying to get pregnant were thrilled to see the Playboy mogul in person."

If the two did have a child, it would be 28-year-old Holly's first, and Hef's fifth. He had two children with first wife Mildred Williams, David Paul and Christie, who is currently the Chairperson of Hef's empire Playbody Enterprises.

Hef and Mildred divorced in 1959, and after dating a succession of Playmates, he married Kimberly Conrad. He had two more children in that relationship, Marston Hefner, who is now 17-years-old, and Cooper Hefner, who is now 16-years-old. Kimberly and Hef haven't actually officially divorced, and so if Holly does get pregnant, the next big question would be, will he finalize that divorce in order to marry Holly?

And then, of course, there is the other big question: what would a Holly pregnancy mean for The Girls Next Door. One has also gotten the distinct feeling - even from Kendra herself - that the other two girls are slowly fading out of the relationship. Would a baby be the final nail in the coffin for Hef's serial dating ways? Only time will tell.

- Leslie Seaton, BuddyTV Staff Columnist