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 ultrasound examinations. Main Outcome Measure(s): The location of ET-associated air bubbles in the uterine cavity and the location of the resultant gestational sec. Result(s): Sixty ETs resulted in 22 pregnancies, and 32 gestational sacs were 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 had 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 approximately 20% implant in other areas. Fertil Sterile 2000;73: 123-5. (C)1999 by American Society for Reproductive Medicine.