What Happens to Embryos That Do Not Attach?

Embryo transfer is the final step in the In vitro fertilization (IVF) process. It consists of depositing the embryo inside the patient’s uterus using a catheter that is inserted through the cervix.

Next, the embryo must implant, which means it must attach to the endometrium to continue its development. This implantation process typically completes 5 to 7 days after the transfer. However, in many cases, embryos do not implant and are reabsorbed by the woman’s body. This embryo reabsorption process does not affect the woman’s tissues, or other embryos that have implanted correctly.

The main causes of implantation failure include:

• Poor embryo quality: Embryos with genetic abnormalities or developmental defects have a lower chance of implanting.
• Low endometrial receptivity: At the time of implantation, the endometrium must have an adequate thickness and structure to facilitate embryo adhesion.
• Immunological and coagulation factors that may interfere with the implantation process.

In case of repeated implantation failure, it is recommended to investigate the underlying causes. Several tests are commonly used for this purpose, such as genetic embryo analysis, endometrial studies, and various hormonal and immunological evaluations.

Non-transferred embryos can be cryopreserved for future attempts, donated to other couples with fertility problems, or allocated for research in certain cases.