Ultrasound-guided miduterine cavity embryo transfer is associated with a decreased incidence of retained embryos in the transfer catheter.

After initiating a policy of ultrasound-guided miduterine cavity embryo transfer (ET) on August 1, 2001, the incidence of retained embryos in the transfer catheter declined significantly from 4.2% (46 of 1,101 ETs) during the time interval January 1, 2000 to July 31, 2001, to 0.7% (6 of 908 ETs) during the time interval August 1, 2001 to December 31, 2002. Blood on the transfer catheter (38% vs. 19%) occurred with significantly greater frequency at ET in which embryos were retained; ETs of > or =4 embryos were more likely to be associated with retained embryos than ETs of <4 embryos (3.7% vs. 2.2%), and both the clinical pregnancy rate (PR) and implantation rate (IR) were lower when embryo retention occurred at ET than they were when embryos were not retained (25% vs. 34% clinical PR; 12% vs. 19% IR).