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Intended Parents

Day 5 Embryo Grading

Day 5 embryo grading describes how a blastocyst has developed and how its cells look under a microscope.

A strong grade can indicate greater potential for implantation, but it cannot tell you whether an embryo will implant or result in a live birth.

That distinction matters if you have good-quality embryos but repeated unsuccessful transfers. Your fertility specialist may need to look beyond the grade and consider embryo genetics, uterine factors and your medical history before recommending another transfer or IVF cycle.

If your embryos remain suitable for transfer but carrying the pregnancy has become the primary barrier, gestational surrogacy may allow you to pursue pregnancy with embryos you have already created.

What Does a Day 5 Embryo Grade Mean?

A day 5 embryo grade describes the development and appearance of an embryo that has reached the blastocyst stage.

With day 5 embryo grading, embryologists typically evaluate how far the blastocyst has expanded and the appearance of two groups of cells.

The widely used Gardner grading system produces grades such as 4AA, 4AB, 5BA or 3BB. Each part of the grade means something different:

Describes blastocyst expansion. Gardner stages run from 1 through 6. A 3 is a full blastocyst, a 4 is expanded, a 5 is beginning to hatch from its surrounding shell and a 6 has hatched.

Describes the inner cell mass (ICM), the cells that develop into the fetus. An A generally indicates more favorable morphology than B or C.

Describes the trophectoderm (TE), the outer cells that contribute to structures including the placenta. An A generally indicates more favorable morphology than B or C.

A 4AA embryo, for example, is an expanded blastocyst with an A rating for both the inner cell mass and trophectoderm.

Understanding how to read embryo grading charts can make grades such as AA, AB, BA and BB easier to discuss with your embryologist.

Grading practices aren’t identical at every embryology lab, so your clinic’s interpretation matters. Ask how your clinic grades embryos and how your specific results compare with the other embryos available for transfer.

Which Day 5 Embryo Grades Have the Best Chance of Success?

Day 5 blastocysts with stronger expansion and favorable inner cell mass and trophectoderm grades generally have better expected outcomes based on morphology.

Grades such as 4AA and 5AA may therefore be considered more favorable than AB, BA, BB or C-containing grades when other relevant factors are similar.

As a general way to interpret the letters:

  • AA: Both the inner cell mass and trophectoderm receive favorable morphology ratings.
  • AB or BA: One receives an A rating and the other a B rating.
  • BB: Both receive B ratings but the embryo may still be suitable for transfer.
  • C-containing grades: These have less favorable morphology in the inner cell mass, trophectoderm or both, but the grade alone doesn’t establish whether pregnancy is possible.

Lower-graded embryos can result in healthy births. A poorer morphology grade generally reflects a lower expected chance compared with a better-graded embryo, not an inability to produce a healthy baby.

Embryo grading and success rates are best understood as probabilities rather than predictions for an individual embryo.

Developmental timing also needs context. Reaching the blastocyst stage on day 6 rather than day 5 doesn’t automatically make an embryo poor quality or unsuitable for transfer.

Your fertility clinic can explain how morphology and developmental timing affect the transfer priority of your remaining embryos.

Is Embryo Grading More Important Than PGT Testing?

No. Embryo grading and PGT testing provide different information, so one isn’t simply a more detailed version of the other.

The easiest way to separate them is by what each evaluates:

  • Embryo grading: Looks at development and morphology, including blastocyst expansion and the appearance of the inner cell mass and trophectoderm.
  • PGT-A: Tests cells biopsied from an embryo for chromosomal abnormalities.

A highly graded embryo isn’t necessarily chromosomally normal. A euploid embryo, meaning PGT-A found the expected number of chromosomes in the sampled cells, can also receive a less favorable morphology grade.

When PGT-A results are available, fertility clinics may consider genetic results alongside morphology and developmental timing when selecting among embryos for transfer.

Understanding what PGT-A evaluates can help you see why a genetic result and an embryo grade aren’t interchangeable.

This distinction becomes particularly useful after failed transfers. Several unsuccessful transfers of untested AA embryos don’t provide the same information as repeated unsuccessful transfers of euploid embryos because favorable morphology cannot rule out a chromosomal issue in an untested embryo.

If you have both embryo grades and PGT-A results, ask your reproductive endocrinologist how each affects the ranking of your remaining embryos.

Why Can a High-Quality Day 5 Embryo Fail to Implant?

A high-quality day 5 embryo can fail to implant because embryo morphology is only one factor involved in implantation. A strong grade doesn’t evaluate everything that has to happen after transfer.

Depending on your circumstances, possible factors can include:

  1. 1

    Chromosomal abnormalities in an untested embryo

  2. 2

    Fibroids, polyps or other uterine cavity conditions

  3. 3

    Endometrial or other uterine factors

  4. 4

    Certain medical conditions

  5. 5

    Factors involving the embryo transfer itself

    Embryo grading can help estimate relative IVF potential, but it cannot predict whether a particular transfer will lead to pregnancy or live birth. The grade describes what an embryologist observes while the embryo develops in the lab.

    It doesn’t establish chromosomal normality or tell your doctor whether conditions in the uterus will support implantation. This helps explain why even a high-quality embryo transfer can be unsuccessful.

    After repeated failed transfers, your fertility specialist may have more reason to investigate factors beyond morphology.

     If good-quality embryos continue to fail, especially when euploid embryos are involved, ask what your transfer history suggests about the embryos versus factors affecting implantation or carrying a pregnancy.

    Not every test offered for repeated implantation failure will provide useful information. Ask what a proposed test is intended to identify and whether the result would change your treatment plan.

    When Multiple Failed Transfers May Point to a Uterine Issue

    Multiple failed transfers of good-quality embryos can prompt a closer evaluation of the uterus, particularly when embryo-related explanations become less likely.

    They don’t prove that the uterus is responsible, but the pattern may give your fertility specialist a reason to investigate before repeating the same transfer approach.

    Depending on your medical and transfer history, that evaluation may consider:

    • Fibroids that affect the uterine cavity
    • Endometrial polyps
    • Uterine adhesions
    • Congenital uterine differences
    • Adenomyosis
    • Other conditions your fertility specialist believes may affect implantation or pregnancy

    The embryos previously transferred make a difference.

    Repeated failed transfers of embryos identified as euploid through PGT-A can raise different questions than failed transfers of embryos selected by morphology alone because an AA grade cannot establish chromosomal normality.

    Some reasons pregnancy can’t be carried may also make another transfer less appropriate even when embryo quality remains promising.

    If a treatable uterine condition is identified, treating it before another transfer may be the appropriate next step.

    If your embryos remain suitable for transfer but your fertility team determines that implantation, maintaining a pregnancy or safely carrying has become the primary obstacle, simply repeating the same approach may not address that obstacle.

    Can You Use Existing Day 5 Embryos With a Gestational Surrogate?

    Yes. Existing frozen day 5 embryos can potentially be transferred to a gestational surrogate if your fertility clinic determines they are appropriate for transfer.

    Moving from IVF to gestational surrogacy doesn’t automatically require you to create new embryos.

    Your existing embryos remain part of the IVF process. Surrogacy changes who carries the pregnancy, not the embryo you have already created.

    The process generally involves several separate pieces:

    For intended parents considering moving from IVF to surrogacy, this distinction matters.

    If you have transferable embryos but implantation, maintaining a pregnancy or safely carrying has become the primary barrier, another egg retrieval may not address that problem.

    Your fertility clinic can determine whether your existing embryos are appropriate for a future transfer and what medical requirements apply before moving forward with a gestational surrogate.

    Does Surrogacy Improve Success if You Already Have Good Embryos?

    Surrogacy may provide a different path to pregnancy when carrying is the primary barrier, but it doesn’t correct a problem originating in the embryo.

    Having a highly graded embryo by itself therefore doesn’t mean a gestational surrogate will improve your chance of success.

    The most useful distinction is what your fertility team believes is preventing pregnancy:

    Transferring the same embryo to a gestational surrogate doesn\'t change its genetics or other embryo-related limitations.

    A gestational surrogate changes who carries the pregnancy, which may address the barrier your medical team has identified.

    More evaluation may be appropriate before assuming either additional IVF or surrogacy is the stronger next step.

    Understanding why IVF keeps failing can help you and your fertility team separate embryo-related problems from barriers related to carrying the pregnancy.

    After multiple failed transfers with embryos that remain suitable for transfer, surrogacy may deserve consideration if your fertility team believes carrying the pregnancy has become the primary barrier.

    We help intended parents understand when embryo quality appears to be the issue and when it may not be.

    That information can help you compare another transfer, additional IVF and gestational surrogacy based on what is most likely preventing success.

    Talk With a Surrogacy Professional About Your Remaining Embryos

    Talking with a surrogacy professional can help you understand how your remaining embryos could fit into a gestational surrogacy journey if carrying has become the primary barrier.

    Before deciding what to do next, there are several pieces of information worth having available:

    A surrogacy professional can then explain the steps that apply when intended parents already have embryos. We can connect you with professionals who can discuss what moving forward may involve.

    When comparing professionals, look for close coordination with fertility clinics, thorough gestational surrogate screening and clear explanations of the medical, financial and legal considerations before you commit.

    That gives you a more useful basis for comparing another embryo transfer, additional IVF and gestational surrogacy using embryos you have already created.

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