What is the difference in embryo grading between 4AA and 3AB, 3BB, 4BB, 4BC (Blastocyst (BL) grade)?

From the Guidelines

In embryo grading for IVF, a 4AA embryo is generally considered the highest quality among the options listed (4AA, 3AB, 3BB, 4BB, 4BC) and should be prioritized for transfer due to its higher implantation potential 1. The grading system typically uses numbers to indicate blastocyst expansion (1-6, with higher numbers showing more expansion) and letters to rate the inner cell mass (first letter) and trophectoderm (second letter), with A being the highest quality, followed by B and C. Therefore, a 4AA embryo has good expansion with excellent quality inner cell mass and trophectoderm, giving it the highest implantation potential. The 3AB would typically be considered the second best option, followed by 4BB, 3BB, and finally 4BC. However, it's essential to consider the latest guidelines from ESHRE, which recommend single embryo transfer (SET) to minimize the risks of multiple pregnancy and complications, regardless of the quality of the embryo 1. Some key points to consider when deciding on embryo transfer include:

• The number of previously failed treatments, which can decrease the odds of ongoing implantation 1
• The risk of ectopic pregnancy, which increases with the number of embryos transferred 1
• The risk of neonatal death and complications, which is higher after double embryo transfer (DET) compared to SET 1
• The importance of counseling patients on the risks and benefits of DET versus SET, including the risks of multiple gestations and pregnancy complications 1. Ultimately, the decision to transfer a 4AA embryo should be made in consultation with a reproductive endocrinologist, taking into account individual patient factors and the latest evidence-based guidelines 1.

From the Research

Embryo Grading

The provided studies do not directly address the comparison of embryo grading 4AA vs. 3AB, 3BB, 4BB, 4BC. However, we can discuss the general aspects of embryo transfer and grading:

• Embryo transfer is a critical step in the overall success of in vitro fertilization (IVF) 2.
• The success of embryo transfer depends on various factors, including the quality of the embryo, the timing of the transfer, and the receptivity of the endometrium 3.
• Embryo grading is an important aspect of IVF, as it helps to select the best embryos for transfer.
• The grading of embryos is typically based on their morphological characteristics, such as the number of cells, the evenness of cell division, and the presence or absence of fragmentation 2.

Comparison of Embryo Grades

While the provided studies do not directly compare the embryo grades 4AA, 3AB, 3BB, 4BB, and 4BC, we can infer that:

• A higher grade embryo (e.g., 4AA) is likely to have a better chance of implantation and live birth compared to a lower grade embryo (e.g., 3AB, 3BB) 4, 5.
• The differences in embryo grades may be related to the metabolic activity and gene expression of the embryos, as suggested by a study on spent embryo culture media 6.
• However, the exact comparison of these specific embryo grades is not addressed in the provided studies.

Factors Affecting Embryo Transfer Success

The success of embryo transfer is influenced by various factors, including:

• The quality of the embryo 4, 5, 3.
• The timing of the transfer 3.
• The receptivity of the endometrium 3.
• The technique used for embryo transfer 2.
• The use of adjunct therapies, such as ultrasound guidance and catheter design 2.