When Reproductive Endocrinologists (REIs) consider accepting donated embryos for intended parents, they consider embryo grades, along with many other important factors to maximize likelihood for a successful, healthy pregnancy and birth:

1. Embryo Quality: Embryo grading is one of the primary considerations, REIs and embryologists assess the embryos based on their developmental stage, cell number, fragmentation, and overall appearance. High-quality embryos are more likely to result in successful implantation and pregnancy.
2. Age of the Egg Contributor: The age of the egg donor at the time of egg retrieval plays a big role. Younger donors typically produce healthier eggs with a lower risk of genetic abnormalities, which can positively impact embryo quality and pregnancy success rates. Older contributors (typically over 35) can level that playing field via PGT-A and their own success rates.
3. Donor Success Rates: The historical success rates of the egg contributor to produce viable embryos that result in successful pregnancies are considered. A donor with a positive track record suggests higher egg quality and embryo development potential. Those who are less successful on their own journey may still have good embryos if their success or failure can be associated with problems carrying the pregnancy, vs. the embryo.
4. Lab Success Rates: The expertise of the embryology team that created the embryos as well as the team that thaws/transfers the embryos is also a real consideration. The quality of equipment and techniques can significantly affect outcomes.
5. Freeze Protocol: The method of embryo freezing can influence the survival rate during thawing and subsequent implantation. Vitrification (fast freezing) is generally considered more successful than slow freezing as it reduces the formation of ice crystals that can damage embryos.
6. Freeze Device: The type of equipment used for freezing embryos can impact the viability of the embryos after thawing. Embryology teams need to be trained on each different freeze device, and mastery of each device may be different.
7. Preimplantation Genetic Testing (PGT): PGT can identify genetic abnormalities in embryos before implantation. Embryos found to be chromosomally normal (euploid) have a higher chance of successful implantation and reduced risk of miscarriage. This is most significant for egg contributors over 35 yrs old. The age of the Intended Parent or Carrier is unrelated, and does not influence the need for PGT-A.
8. Donor Health History: A comprehensive health history of the genetic contributors includes genetic, medical, and psychological assessments. A thorough screening helps ensure that potential genetic or health risks are minimized, and that Intended Parents are prepared for managing possible genetic conditions.
9. Intended Carrier: The medical history and physical condition of the intended carrier (surrogate or intended mother) are evaluated to determine the likelihood of a successful pregnancy. Factors such as uterine health, hormonal levels, and overall reproductive health are taken into consideration separately from embryo evaluation.
10. Legal and Ethical Considerations: REIs also consider legal and ethical aspects, such as ensuring proper consents from both the donors and intended parents, adherence to regulations, and ethical standards in the field of assisted reproduction.
11. Communication and Counseling: Open and clear communication between the clinic, the donors, and the intended parents help to facilitate a successful donation and long term information sharing. Counseling and support are often provided to help all parties navigate the emotional and psychological aspects of the process.

Reproductive providers evaluate embryo donations based on their own criteria and priorities. Intended parents should have open discussions with their chosen clinic to understand the specific factors that will influence their decision-making process, and should get second opinions when appropriate to ensure the best decision for their family.