During the ET procedure following In Vitro Fertilization (IVF), bracketing the transfer media containing the embryo(s) with air bubbles within the transfer catheter is a safe technique that may allow ultrasonographic tracking of the embryos immediately following transfer into the uterine fundus. On occasion, the air bubble that is expulsed with the embryo(s) is subsequently seen to follow the transfer catheter toward the cervix as the catheter is withdrawn. We set out to determine whether an ET in which this bubble movement is observed has a lower prognosis for pregnancy than does an ET where no bubble movement is observed.