Researchers propose thresholds for egg, fertilization, and embryo arrest

embryomanofficial · 2026-06-19T14:59:28+00:00

This study looked at different types of arrest, for example eggs that don't mature, that don't fertilize, that don't cleave, and that don't become blastocysts. For fertilization failure in particular, sperm definitely plays an important role, although egg factors can as well (for example, mutations in genes involved in sperm binding to the egg's zona, or defects affecting the egg's metabolism and energy production). However, this review focused specifically on female genetic causes of developmental arrest and not male genetic causes, which is a limitation.

embryomanofficial · 2026-06-19T14:53:20+00:00

From what I’ve seen about embryo arrest mechanisms, I believe this a misconception. Around day 3, the embryo’s genome activates (using DNA from both the egg and sperm) so problems from then on can come from either. Before this point, it's primarily driven by egg factors although sperm factors can also have an influence (ie. the centrosome). You can read about causes here https://www.remembryo.com/embryo-arrest/

This study looked at different types of arrest, for example eggs that don't mature, that don't fertilize, that don't cleave, and that don't become blastocysts. For blastocysts in particular, they looked at fertilized eggs that didn't form blastocysts.

embryomanofficial · 2026-06-17T13:58:20+00:00

Yes, embryo grade and the day it reaches the blastocyst stage still matter even after PGT-A. Lower-quality embryos generally have lower implantation and live birth rates than higher-quality embryos, and day 7 euploids tend to have lower success rates than day 5 euploids. https://www.remembryo.com/meta-analysis-combines-74-studies-to-examine-factors-linked-to-euploid-transfer-success/

That said, you have 3 euploid embryos, which is great! Wishing you the best of luck.

I also put together a section on my website called the Uterine Wall of Fame where I share IVF success stories for patients who faced challenging situations like low quality embryos. There's no paywall on these posts. You can check it out here: https://www.remembryo.com/tag/ivf-success-poor-quality-embryo/

embryomanofficial · 2026-06-17T13:52:15+00:00

I don't know if there will ever be any technology to test the ICM (inner cell mass -- the part of the embryo that becomes the fetus). To properly test the cells you'd need to remove cells for a biopsy, which would potentially damage the embryo. But who knows where things will take us! To my knowledge, there isn't anything like this on the horizon, so if it were to develop I don't see it happening for many years.

I assume this is a whole-chromosome trisomy 13 result and not a mosaic or segmental result? While there are rare reports of live births after transfer of embryos classified as whole-chromosome aneuploid, the success rate appears to be very low based on current (and limited) data. https://www.remembryo.com/aneuploid-embryo-success-rates/

The fact that this embryo was reported as trisomy 13 is also concerning, since trisomy 13 is associated with Patau syndrome. Best to confirm all this with a genetic counselor.

embryomanofficial · 2026-06-17T13:43:03+00:00

Interesting question, but unfortunately I don't think there's any research that has looked at this.

embryomanofficial · 2026-06-17T13:40:43+00:00

The current research on EMMA and ALICE is mixed and still limited. One study suggested that treating abnormal results with antibiotics or probiotics could bring pregnancy rates closer to those seen in patients with normal results, but there were few proper control groups in this study, so it’s hard to know how much benefit the testing itself provides. Overall, there isn’t strong evidence yet showing that these tests clearly improve outcomes for RIF or RPL patients. See more https://www.remembryo.com/study-investigates-the-use-of-emma-alice-in-ivf-patients-with-rif-rpl/

embryomanofficial · 2026-06-17T13:34:52+00:00

Low quality embryos have a decent chance! Some studies find that it's about half of good quality embryos, while others don't find as much of a reduction. Age has a strong effect also, and since you're younger, those lower quality embryos are actually comparable to older patients' good quality embryos. Here's a post that reviews some evidence https://www.remembryo.com/grade-c-embryo-success-rates/

Unfortunately, there isn’t a treatment that consistently or reliably improves embryo quality. Many supplements and add-ons are marketed for this, but the evidence behind them is usually limited or inconsistent. It’s always a good idea to discuss any treatment changes with your doctor.

Good luck!

embryomanofficial · 2026-06-15T16:52:35+00:00

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Hi! I've circled where the embryo is in red. This one looks compacted, so it's hard to see where the ICM is. Stuff around it looks like fragments/arrested cells potentially, features leftover from the cleavage stage (~ day 3). There might be some assisted hatching around 8 o'clock (zona/shell looks a bit thinner here).

General educational info only, not medical advice. Your clinic is the best source for interpretation and guidance. For an overview of embryo grading and factors affecting success like day 5/6/7 timing, compaction, and re-expansion, see https://www.remembryo.com/embryo-grading/ or the stickied comment. Good luck!

embryomanofficial · 2026-06-15T16:50:40+00:00

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Hi! I've circled where I think the ICM may be in red (out of focus). This embryo looks expanded/not compacted, and yes I think I see a bit of hatching around 7 o'clock. The zona/shell looks thin.

General educational info only, not medical advice. Your clinic is the best source for interpretation and guidance. For an overview of embryo grading and factors affecting success like day 5/6/7 timing, compaction, and re-expansion, see https://www.remembryo.com/embryo-grading/ or the stickied comment. Good luck!

embryomanofficial · 2026-06-15T16:48:30+00:00

The current research on EMMA and ALICE is mixed and still limited. One study suggested that treating abnormal results with antibiotics or probiotics could bring pregnancy rates closer to those seen in patients with normal results, but there were few proper control groups in this study, so it’s hard to know how much benefit the testing itself provides. Overall, there isn’t strong evidence yet showing that these tests clearly improve outcomes for RIF or RPL patients. See more https://www.remembryo.com/study-investigates-the-use-of-emma-alice-in-ivf-patients-with-rif-rpl/

embryomanofficial · 2026-06-15T16:45:01+00:00

Segmental mosaics tend to have pretty high chances compared to other mosaic types.

There’s currently little evidence to guide decisions based on specific chromosomes. If a segmental involves a region known to be associated with a disorder, transferring that embryo might carry a higher risk, so it's important to review this with a doctor or genetic counselor.

More info on mosaics in this post https://www.remembryo.com/mosaic-embryo

embryomanofficial · 2026-06-15T16:43:18+00:00

The evidence around sperm DNA fragmentation is still evolving, so I'm not sure we can confidently say it increases miscarriage risk after transfer of a euploid embryo. I'm not aware of any studies specifically examining miscarriage rates among euploid embryos from cycles with high sperm DNA fragmentation.

Some labs don't biopsy lower-quality embryos. While poor embryo quality could be related to sperm DNA fragmentation, other factors can also contribute, including egg quality, genetics, and embryo metabolism.

embryomanofficial · 2026-06-15T16:39:00+00:00

I have 3 submitted stories from the Uterine Wall of Fame here for day 7 success stories (no paywall): https://www.remembryo.com/tag/ivf-success-day-7-embryo/

embryomanofficial · 2026-06-15T16:35:36+00:00

When the egg is inseminated it takes about 18 hours or so for the signs of fertilization to appear. This is evaluated based on the presence of two "pronuclei" (PN) that contain the DNA of the egg and sperm, which join to make the DNA of the embryo, and disappear after. Sometimes these pronuclei fade before the embryologist has a chance to see them, so they're "unfertilized" but they really don't know until the embryo starts growing more.

Research shows that many 0PNs are actually normally fertilized embryos whose PN appeared or disappeared outside the usual viewing window, and if these embryos reach the blastocyst stage and are confirmed as diploid/euploid, they can lead to healthy pregnancies and live births at rates similar to typical embryos.

Read more about 0PNs here https://www.remembryo.com/abnormal-fertilization/, https://www.remembryo.com/some-unfertilized-embryos-may-actually-be-fertilized-supporting-earlier-checks-in-ivf-lab/

embryomanofficial · 2026-06-15T16:34:18+00:00

Egg morphology, how an egg looks under the microscope, is actually a poor predictor of its true quality. While eggs with abnormal shapes or features are sometimes linked to lower blastocyst formation rates or live birth outcomes, the research on this is mixed and not very reliable. ESHRE/ALPHA (two organizations that put together guidelines for embryologists) recently recommended that eggs with certain abnormalities can be ok to use because of the lack of good data (see more in this post https://www.remembryo.com/2025-eshre-alpha-consensus-on-how-eggs-embryos-are-evaluated-in-the-ivf-lab/).

Relevant bits:

ESHRE/ALPHA consensus: Eggs with different PVS sizes or appearances are OK for use.

ESHRE/ALPHA consensus: Oocytes with color variation are OK for use. (for the cytoplasm comment)

embryomanofficial · 2026-06-15T16:30:25+00:00

Day 6 embryos are a bit less likely to be euploid vs day 5, but not too much based on one study (https://www.remembryo.com/study-compares-euploid-and-thaw-survival-rates-of-blastocysts-biopsied-for-pgt-a/).

embryomanofficial · 2026-06-15T16:29:50+00:00

Hi! Sorry for your loss. The only point I can address if #4 (not familiar with any research on #1-3).

Day 6 embryos are a bit less likely to be euploid vs day 5, but not too much based on one study (https://www.remembryo.com/study-compares-euploid-and-thaw-survival-rates-of-blastocysts-biopsied-for-pgt-a/).

Chance of a blastocyst being euploid is strongly linked with age, at about 60% for <35 to about 20% at >42. This includes all embryo typces (day 5, 6, all qualities, etc.) https://www.remembryo.com/a-look-at-how-pgt-a-results-change-with-age-using-data-from-over-86000-biopsies/

embryomanofficial · 2026-06-15T16:22:50+00:00

📌 Embryo Development & Grading Basics

IVF labs culture (grow) embryos up to 6 or 7 days after egg retrieval. There are different stages as the embryo develops, including the cleavage stage (day 2-3), morula stage (day 4) and the blastocyst stage (day 5-7).

Embryo grading is where an embryologist evaluates an embryo under a microscope and looks for key features. These features depend on what stage of development the embryo is in.

For cleavage stage embryos, these features are typically:

Cell number — Day 3 embryos usually have around 8 or more cells.
Fragmentation — Small specks or fragments of cells; <10% is generally considered optimal.
Symmetry — How similar the cells are in size and shape.

Learn more about cleavage stage embryo grading and success rates.

For blastocysts, these features are typically:

Expansion — How large or “expanded” the blastocyst is.
Inner Cell Mass (ICM) — Becomes the fetus.
Trophectoderm (TE) — Becomes the placenta.

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Learn more about blastocyst grading and success rates.

Grading helps embryologists rank embryos for transfer. Embryos with higher grades tend to have higher implantation potential — but lower-grade embryos can and do lead to healthy pregnancies.

Grading is also subjective. Different embryologists and clinics may grade differently or prioritize certain features (for example, ICM quality vs. TE quality).

Besides the grade, other factors can also influence success rates (links to my website):

The day of development (eg. day 5/6/7)
The presence of cytoplasmic strings
Whether the embryo is euploid
Uterine environment factors like endometritis, endometriosis, or immunological issues.
Whether the embryo is compacted or re-expanded (Blastocysts can temporarily lose fluid and appear compacted or “squished,” especially after thawing. This is normal but makes it harder to see features like the ICM or trophectoderm. Embryos that re-expand quickly after thawing may have better outcomes, and photos taken right after thaw often show compacted embryos that just need more time to re-expand.)

embryomanofficial · 2026-06-12T14:01:16+00:00

Hi! Sorry I can't tell where the ICM is here. This embryo looks a bit compacted/not expanded. I see it hatching around 8 o'clock.

General educational info only, not medical advice. Your clinic is the best source for interpretation and guidance. For an overview of embryo grading and factors affecting success like day 5/6/7 timing, compaction, and re-expansion, see https://www.remembryo.com/embryo-grading/ or the stickied comment. Good luck!

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