'Bold And The Beautiful' Spoilers: Steffy And Liam React To Her Pregnancy News

It's a moment that should be giving them both immense joy, but news that she is pregnant will instead cause Steffy to panic on the Monday, Dec. 18 episode of "The Bold and the Beautiful."

During a routine doctor's visit on the CBS soap, Steffy (Jacqueline MacInnes Wood) and Liam (Scott Clifton) learned that she was actually pregnant, and the news was something that initially shocked them both. Due to Steffy's history, they felt there was no chance she actually would get pregnant again, so hearing she was gave them both joy. However, Steffy quickly saw her joy turn to fear, as she flashed back to her recent sexual romp in bed with Liam's father, Bill (Don Diamont).

Now, as Liam is in a celebratory mood because he feels he will get to be a father, and that he and the woman he loves will be parents together, Steffy will be less enthused, because she fears he may not be the one who got her pregnant after all.

"I'm going to be a dad!" He says excitedly in a preview clip.

"I didn't think that this would ever happen for us, ever," Steffy mumbles.

"And yet, it's happened," Liam exclaims.

Now, Steffy will be worried about what could happen in the future. She hasn't told Liam, or anyone else, about the night in the guesthouse with Bill, and doesn't plan to. However, it won't be long before news of her pregnancy spreads—and Bill himself finds out.

Steffy's fears will not only be that she has to pass off Bill's potential child as Liam's, but she will also fear how Bill will react. Since they slept together, he has been insisting to her that they should be together as a couple, and they they're in love. She has in turn insisted that they aren't, and she wants to be with Liam. However, if Bill hears she's pregnant, and the baby could be his, he will even less likely to back down, and the truth could come out after all.

"The Bold and the Beautiful" airs weekdays at 1:30 p.m. EST on CBS.