As part of the overall planning for Mexico surrogacy, many families feel confused when they actually receive an embryo report, often staring at a series of numbers and letters without knowing what they mean. What do 4AA, 5AB, and 6BB actually mean? Which embryo is better? If the report also includes information such as Day 5, Day 6, and PGT-A, how should it be interpreted?
What Does an Embryo Report Usually Show?
After embryos develop to the blastocyst stage, laboratories typically evaluate their morphology from multiple perspectives. Common blastocyst grading systems include the Gardner grading system and the SART grading system. The Gardner system mainly evaluates the degree of blastocyst expansion, the inner cell mass (ICM), and the trophectoderm (TE).
If the report shows “5AA,” it can first be broken down into three parts. The first number represents the stage of blastocyst expansion and hatching, while the two letters correspond to the inner cell mass and trophectoderm, respectively.
What Do Numbers 1 to 6 Mean?
In the Gardner grading system, the numbers mainly describe the degree of blastocyst expansion and whether the blastocyst is hatching. A higher number does not simply mean that the “embryo is better”; rather, it indicates a different stage of blastocyst development and expansion.
For example, 3 represents a full blastocyst, 4 represents an expanded blastocyst, 5 represents a hatching blastocyst, and 6 represents a fully hatched blastocyst.
Therefore, when you see 4, 5, or 6, you should not interpret them directly as “higher scores.” The number and the A, B, or C letters represent different aspects and need to be interpreted together.
How Should AA, AB, and BB Be Interpreted?
The first letter usually represents the inner cell mass, which is the group of cells that will eventually form the fetus; the second letter represents the trophectoderm, which is involved in the formation of the placenta.
A generally indicates a larger number of cells with a more compact and complete arrangement; B indicates an intermediate level of cell number and organization; C indicates fewer cells or a relatively less ideal arrangement. The grading criteria published by ASRM also clearly evaluate the inner cell mass and trophectoderm separately.
Therefore, when looking at reports such as 4AA, 5AB, and 5BB, you should not focus only on the number at the beginning. A complete interpretation requires considering both the blastocyst expansion stage and the morphology of the ICM and TE.
What Is the Difference Between Day 5 and Day 6?
Embryo reports often include information such as Day 5 and Day 6, referring to the amount of time required for the embryo to develop to the blastocyst stage.
Some embryos can form blastocysts on Day 5, while others may require Day 6 or even later. Simply seeing Day 6 does not mean that the embryo is necessarily poor. What matters is the blastocyst morphology, subsequent testing results, and the overall embryo development process.
How Should You Read a Report That Includes PGT-A Results?
If the embryo has undergone PGT-A, the report contains more than morphological grading. Morphological grading mainly describes the embryo’s appearance and developmental status under a microscope, while PGT-A provides information about the embryo’s chromosomes. These are two different levels of evaluation.
Therefore, when planning embryos for Mexico surrogacy, if embryo culture and PGT-A testing have already been completed, the final transfer order should not be determined solely according to “AA,” “AB,” or “BB.” It should be arranged based on the morphological grade, testing results, and a comprehensive assessment by the doctor and embryology laboratory.
For each individual cycle, the interpretation should also be based on the specific circumstances and laboratory report. Located in the heart of Mexico City, Power Fertility Clinic is a fully licensed reproductive center operated by a U.S. assisted reproductive organization, just 500 meters from the U.S. Embassy and compliant with U.S. FDA standards. Power IVF provides one-stop services, from egg and sperm donation to third-party reproduction, covering the full process of egg freezing and IVF in the United States. The clinic has advanced equipment and an experienced team specializing in IVF-PGT (PGT-A), helping families preparing for pregnancy pursue better reproductive outcomes. Mexican law supports gender selection and the importation of frozen reproductive tissues, including sperm, eggs, and embryos, and is open to all groups, including single individuals and LGBTQ families. Power IVF is licensed to receive frozen samples from overseas, helping ensure the safety and continuity of your reproductive plan.
