Where does the embryo implant after embryo transfer in humans?

Objective: To investigate where human embryos implant after ET. Design: Prospective analysis. Setting: University hospital. Patient(s): Sixty infertile women without uterine fibroids, a major uterine anomaly, or a history of cesarean section. Intervention(s): Transabdominal and transvaginal three-dimensional ultrasou nd examinations. Main Outcome Measure(s): The location of ET-associated air bubbles in the u terine cavity and the location of the resultant gestational sec. Result(s): Sixty ETs resulted in 22 pregnancies, and 32 gestational sacs we re located. Twenty-six of the 32 embryos were within or between the area in which the catheter tip was situated and the area over which air bubbles ha d spread immediately after ET. Conclusion(s): In cases of pregnancy achieved through ET, approximately 80% of embryos implant in areas to which they initially are transferred and ap proximately 20% implant in other areas. Fertil Sterile 2000;73: 123-5. (C)1 999 by American Society for Reproductive Medicine.