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We report the discovery a bipolar molecular outflow centered on the ultracompact HII (UCHII) region G45.12+0.13 that we have mapped in the CO 2$\to$1, 3$\to$2, 6$\to$5, $^{13}$CO 2$\to$1 and C$^{18}$O 2$\to$1 transitions at the Caltech Submillimeter Observatory. The north-south bipolar structure appears consistently in all of the $^{12}$CO lines as well as in the $^{13}$CO line. At a distance of 9.5~kpc, the outflow is 3.0~pc in length with a characteristic velocity of 7.0~km~s$^{-1}$ and a dynamical timescale of 2.1~$\times$~10$^5$ yr. Since the dynamical age of the UCHII region under the strong shock approximation is only 2.6~$\times$~10$^4$~yr, these measurements imply that $\sim90$\% of the molecular outflow expansion occurred prior to the birth of the UCHII region. Alternatively, the discrepancy in timescales could be taken as additional evidence for the inhibited expansion of UCHII regions first proposed by Wood \& Churchwell (1989) on statistical grounds.
