Embryo Grading; what you need to know.

Embryo grading is indeed a crucial aspect of the science behind successful gestational surrogacy. The grading process allows reproductive specialists to assess the quality and viability of embryos before implantation, increasing the chances of a successful pregnancy while minimizing the risks associated with multiple births.

Embryo grading typically occurs at two stages: three days after fertilization (cleavage-stage embryos) and five days after fertilization (blastocysts). Let’s delve into the grading process at each stage:

  1. Cleavage-stage embryos (graded on a scale of one to four): At the three-day mark, embryos are examined under a microscope to determine if they have undergone the appropriate cell division. The number and uniformity of cells are considered in the grading process. Generally, only embryos graded as one or two are selected for implantation. Grade three embryos may be used under certain circumstances, such as if other factors indicate viability or if grade one or two embryos are unavailable.
  2. Blastocysts (graded from A to D): By the fifth day, the embryos have developed into blastocysts. At this stage, grading becomes more nuanced, using a combination of two criteria: the expansion of the embryo (represented by a letter from A to D) and the quality of the inner cell mass and the trophectoderm (represented by a second letter from A to C). The ideal embryo, often referred to as “perfect,” would be graded as 4AA, indicating excellent expansion and quality. However, it’s important to note that grading involves various factors, and the specific grading system may differ slightly between clinics or specialists. The reproductive endocrinologist closely monitors the embryos to determine which ones have the highest chance of resulting in a successful pregnancy.

Accurate grading is essential for both intended parents and gestational surrogates as they share the common goal of a successful outcome. During the contract stage, discussions about embryo transfer and the possibility of selective reduction (if multiple embryos implant) may take place. These conversations help establish mutual understanding and ensure that the parties involved are aligned in their expectations.

If you have further questions about the science of embryo grading or any other aspect of gestational surrogacy, it is advisable to refer to previous posts or reach out to Surrogate Solutions or a reproductive specialist for more information.


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