<P> As the season ends, Blair crowns Jenny the new queen of Constance Billard School . In the season finale, it is discovered that Blair slept with Chuck's uncle Jack and that Chuck had slept with Vanessa Abrams . Chuck then departs for Europe . He later returns to New York and reconciles with Blair while declaring his love for her, and the two finally begin a committed relationship . </P> <P> In the third season, Blair joins Vanessa, Georgina, and Jenny's brother Dan at NYU . Much of her story line concerns her inability to attain her previous status at her new school . She finds emotional support from her mother, as well as Chuck . However, she and Chuck separate once again when Blair feels that he manipulated her while competing with his uncle (Chuck made a deal with Jack that Blair could sleep with him and in exchange, Chuck gets his hotel back that Jack initially stole to' destroy Chuck'). </P> <P> She later transfers to Columbia University, and learns that an emotionally reformed Chuck was responsible for her enrollment . They later team up as part of a role - playing scheme to help Serena's mother and Chuck's adopted mother, Lily . In the season finale, Chuck attempts to propose to Blair, but is interrupted by Dan, who reveals that Chuck had slept with Jenny . Two weeks later, Blair and Serena depart for Paris intending to spend the summer together . </P> <P> In Season 4, Blair and Chuck become competitive once again, but eventually resume their sexual relations before recognizing their love for one another . When the relationship interferes with their business interests, she and Chuck break up once more . Chuck promises he'll wait for her, and both affirm their belief that their love will reunite them in the end . </P>

When does blair have her baby with chuck