Carrie Underwood gave her fans a sneak peek at her postbaby bikini body when she posted a Summer-infused vacation selfie to Instagram on Tuesday. Carrie, who gave birth to son Isaiah in late February, captioned the photo, "Vacation selfie. #IKnowImLame." While it's not clear where the singer is relaxing ahead of her first Mother's Day, she looks happy and healthy while lounging on what appears to be a white and yellow beach towel. She then posted a cute photo of herself on a balcony, with the caption, "Palm bliss . . ." And it's no surprise that Carrie, who wed professional hockey player Mike Fisher in 2010, is already back in a bathing suit. The fit singer recently launched her own athleticwear line, Calia by Carrie Underwood. See the cute photos above and below, then check out some other celebrities who will be celebrating their first Mother's Days this Sunday.