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Intended Parents

IVF Embryo Grading

IIVF embryo grading describes how an embryo looks and develops in the laboratory.

 Fertility clinics use these grades to compare embryos for transfer or freezing, but a grade can’t tell you whether an embryo will implant or become a healthy baby.

If you’re creating embryos for a future surrogacy journey, the grade is one piece of a larger medical picture. Understanding how embryo grading works can help you interpret the information your embryology team gives you about your embryos.

PGT results, the age of the person whose eggs were used, the number of embryos available and the gestational surrogate’s medical evaluation can also influence transfer planning.

Your fertility clinic can explain how much weight it gives embryo grades compared with these other factors when choosing an embryo for transfer.

Day 5 Blastocyst Grading Explained

Day 5 blastocyst grading describes the embryo’s stage of expansion and the appearance of two groups of cells.

Many fertility clinics use the Gardner system, which produces grades such as 5AA, 4AB and 3BB.

Here’s what each part describes:

  • Number

    The inner cell mass (ICM), which develops into the fetus. An A generally indicates more favorable morphology than a B or C.

  • First Letter

    The inner cell mass (ICM), which develops into the fetus. An A generally indicates more favorable morphology than a B or C.

  • Second Letter

    The trophectoderm (TE), which contributes to the placenta. An A generally represents more favorable morphology than a B or C.

    Put those three parts together and common grades can be read like this:

    These examples make embryo grading charts easier to interpret because each character describes a specific feature rather than an overall pass-or-fail score.

    A 3BB embryo may still be considered for transfer, while a 5AA embryo can still fail to implant.

    Among otherwise comparable blastocysts, a fertility clinic will generally prioritize embryos with more favorable morphology, such as an AA-grade embryo, over embryos with lower morphological grades.

    But there isn’t one universally best grade for every frozen embryo transfer because PGT results, developmental timing and the clinic’s assessment of the full embryo cohort can change transfer order.

    Grading also involves visual assessment, and laboratories can differ in how they assign or report grades.

    When you’re planning a future surrogate embryo transfer, ask your own embryology team how it ranks the embryos you have rather than assuming a grade from one clinic means exactly the same thing at another.

    Day 3 Grading Explained

    A Day 3 embryo is usually at the cleavage stage, the basic difference is:

    • Day 3 grading: Looks primarily at cleavage-stage development, including cell number, fragmentation, cell symmetry and multinucleation.
    • Day 5 grading: Looks at a blastocyst’s expansion, inner cell mass and trophectoderm.

    Around eight cells on Day 3 is generally considered a favorable developmental benchmark, although embryos with fewer or more cells can continue developing.

    For a Day 3 embryo, the laboratory may evaluate:

    • Fragmentation

      Small fragments can appear between dividing cells. Lower percentages of fragmentation are generally considered more favorable.

    • Cell symmetry

      Embryologists look at whether the cells, called blastomeres, are relatively even in size.

    • Multinucleation

      More than one nucleus within a blastomere can be an unfavorable finding.

    • Developmental pace

      The embryologist considers whether the embryo is dividing at the expected rate for that point in development.

      Day 3 grading isn’t standardized across every fertility laboratory. This overview of embryo grading for surrogacy provides additional context for intended parents considering how their embryos could fit into future transfer planning.

      One clinic may use letters, another may use numbers and another may use its own scoring system.

      If your embryos were created at more than one clinic, don’t assume that similarly named grades represent exactly the same assessment.

      For example, an eight-cell embryo with evenly sized cells, little fragmentation and no observed multinucleation would generally have stronger Day 3 morphology than a slower-developing embryo with substantial fragmentation and irregular cells.

      Embryos that don’t fit the strongest description can still continue developing.

      Clinics may also culture embryos to the blastocyst stage when appropriate because additional development gives the embryology team more information for embryo selection.

      Day 3 transfer may still be considered in some cases, including when relatively few embryos are available and the fertility team recommends an earlier transfer.

      Does a Better Embryo Grade Mean Higher IVF Success?

      Yes, better embryo morphology is generally associated with greater implantation and pregnancy potential, but a better grade doesn’t guarantee IVF success. The grade alone can’t predict the outcome of an individual transfer.

      Success can also be affected by:

      • The age of the person whose eggs were used
      • Embryo genetics
      • Uterine and endometrial health
      • Transfer timing and technique
      • Fertility laboratory quality

      Understanding embryo grading success rates can help you put a grade in context rather than treating it as a stand-alone prediction.

      Lower-graded embryos can result in healthy births, while highly graded embryos can fail to implant.

      Having only lower-graded embryos also doesn’t automatically rule out surrogacy if your fertility clinic still considers those embryos appropriate for transfer.

      What lower grades may change is the clinic’s expectations for each transfer and how you plan around the number of embryos available.

      For a surrogate embryo transfer, don’t assume the embryo with the highest morphology grade will automatically be transferred first.

      Your fertility clinic may give greater weight to PGT results or consider developmental timing and other embryo characteristics.

      Before a surrogate transfer, ask your clinic:

      1. 1

        Which embryo would you recommend transferring first?

      2. 2

        Why does that embryo rank ahead of our others?

      3. 3

        How much weight are you giving its grade versus its PGT result?

      4. 4

        How does our total number of transferable embryos affect the transfer plan?

        Those answers tell you more about your actual situation than the morphology grade alone.

        Embryo Grade vs. PGT Testing: Which Matters More?

        Neither embryo grade nor PGT results universally matter more. They provide different information that a fertility clinic can consider together when selecting an embryo for transfer.

        The simplest distinction is:

        • Embryo grading tells you: How the embryo looks and develops under laboratory assessment.
        • PGT tells you: Information about specific genetic or chromosomal characteristics, depending on the type of testing performed.

        Embryo genetic testing results therefore shouldn’t be treated as another form of embryo grading.

        PGT-A, for example, screens biopsied embryo cells for chromosome-number abnormalities.

        An embryo can receive a strong morphological grade and still have an aneuploid PGT-A result. A lower-graded embryo can receive a euploid result.

        That difference can affect which embryo a fertility clinic recommends transferring first. When PGT-A results are available, the clinic can consider chromosomal status along with morphology and other clinical information.

        Among embryos with similar PGT results, morphology may still help the clinic decide transfer order.

        PGT doesn’t guarantee implantation or a healthy birth, and whether testing is appropriate depends on the circumstances.

        If you’re creating embryos for surrogacy, ask your reproductive endocrinologist whether PGT would change the clinic’s transfer recommendation based on the age of the person whose eggs were used, embryo availability and treatment history.

        Why Can High-Quality Embryos Still Fail to Implant?

        High-quality embryos can still fail to implant because embryo morphology is only one part of implantation.

        Even an embryo with a strong grade or a euploid PGT-A result doesn’t have a guaranteed chance of becoming a pregnancy.

        Depending on the individual case, factors that may warrant consideration include:

        • Uterine abnormalities
        • Adenomyosis
        • Endometrial or hormonal factors
        • Transfer timing
        • Transfer technique
        • Embryo-related factors not identified through routine morphology grading or PGT-A

        Understanding why IVF can fail helps separate embryo grade from the other factors involved in implantation. Information about high-quality embryo transfer success can also provide context for why a favorable grade doesn’t guarantee a successful transfer.

        Immune factors are sometimes discussed in cases of repeated implantation failure, but proposed immune testing and treatments aren’t uniformly supported for every patient.

        If your clinic recommends this type of evaluation, ask what condition it suspects, what the test can establish and how a positive or negative result would change treatment.

        One failed transfer by itself also doesn’t establish why implantation didn’t occur.

        When unsuccessful transfers repeat, your reproductive endocrinologist can look at your embryo history, uterine evaluation and previous transfer records for evidence that may change the next treatment recommendation.

        This review matters before assuming that a gestational surrogate will solve the problem. If the suspected barrier is related to carrying the pregnancy, surrogacy may address that factor.

        If the evidence instead points to the embryos, changing who carries the pregnancy doesn’t improve embryo quality.

        When Surrogacy May Be Worth Discussing After Failed IVF

        Surrogacy may be worth discussing after failed IVF when medical evidence suggests that carrying the pregnancy is a significant barrier or risk rather than assuming embryo quality is the only explanation.

        This distinction is especially relevant after repeated unsuccessful transfers or pregnancy losses involving embryos that received encouraging grades.

        Depending on the diagnosis and individual history, a surrogacy conversation may arise with:

        • Recurrent implantation failure

        • Recurrent pregnancy loss

        • Significant uterine scarring

        • Adenomyosis

        • Uterine structural abnormalities

        • A medical condition that makes pregnancy unsafe

          Learning about surrogacy after failed IVF as a path forward can help you understand why changing who carries the pregnancy may address some medical barriers but not others.

          Surrogacy doesn’t improve embryo quality. If embryo quality appears to be the main concern, transferring the same embryos to a gestational surrogate doesn’t correct that problem.

          If your embryos remain appropriate for transfer but your medical team believes carrying the pregnancy is limiting success, surrogacy may address a barrier that another transfer to you would not.

          Ask your reproductive endocrinologist what evidence suggests transferring to a gestational surrogate could change the medical picture compared with another transfer to you.

          The answer can help you decide whether speaking with a surrogacy professional is an appropriate next step.

          Explore Whether Your Embryos Could Be Used in a Surrogacy Journey

          If you still have embryos after unsuccessful IVF, their grades can help your fertility clinic plan future transfers, but the grades don’t determine whether surrogacy is the right next step.

          The decision depends on what your clinic believes about the embryos you have and whether carrying the pregnancy appears to be limiting success or creating an unacceptable medical risk.

          Understanding the next steps after failed IVF can help identify what still needs to be answered before deciding whether surrogacy belongs in that conversation.

          Our goal is to help you make informed decisions rather than relying on grades, success-rate headlines or marketing claims.

          For a future surrogacy journey, embryo grading should be considered alongside PGT results, the age of the person whose eggs were used, embryo availability and the gestational surrogate’s medical evaluation.

          Before deciding what comes next, ask your fertility clinic:

          Those answers give you a stronger basis for deciding whether another IVF attempt, further medical evaluation or a conversation with a surrogacy professional fits your situation.

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