As it turns out, it is Puck's baby when he cornered her about this.
Puck: Well lately I've been thinking about us. I cant imagine how proud I am of you and watching your career take off. Puck got down on one knee opening a Tiffany's box. Puck looks jealous when Quinn goes to practice on sitting on Finn's lap. Mercedes tells him to not disturb Quinn any further, because he has done enough.In the end, when the ND members sing 'Lean on Me' to Finn and Quinn to console them, Puck smirks at Quinn when he sings the line - "Call me".Showmance Quinn laughs and smiles at Puck after he slushies Rachel.Preggers Quinn tearfully reveals that she is pregnant to Finn saying that the baby is his.Mash-Up Puck stares at Quinn as she walks away from Finn when Will is performing 'Bust-A-Move'.