Researchers in 2024 report on live births after segmental aneuploid transfers, finding that they have similar rates as high level mosaic segmental aneuploids.
PGT-A can determine whether an embryo is euploid and has the right number and structure of chromosomes. In whole chromosome aneuploids, entire chromosomes are missing or duplicated, while segmental aneuploids have large pieces of chromosomes affected. These embryos are typically not transferred.
Check my complete guide to PGT-A to get more background on PGT-A (aka PGS testing) and understand how segmental aneuploidies are reported.
🔗 Original studies are referenced in this post or within the linked Remembryo posts.
💡 Reminder: Terms underlined with a dotted black line are linked to glossary entries. Clicking these does not count toward your paywall limit.
There is limited data on the success rates of segmental aneuploids, with some studies showing that rebiopsying these embryos can lead to reclassification to a mosaic.
A new study by Besser et al. (2024), reviewed in this post, reported pregnancy outcomes for transfers involving segmental aneuploids.
There were a total of 25 frozen transfers:
- 17 were single embryo transfers involving a segmental aneuploid.
- 6 were double transfers involving a segmental aneuploid and a mosaic.
- 2 were double transfers involving a segmental and a euploid.
Out of 25 embryo transfers, 6 resulted in live births from segmental aneuploid embryos, achieving a 24.0% live birth rate. Five live births originated from single segmental aneuploid transfers, while one came from a double transfer, identified through the sex of the segmental aneuploid embryo. Five babies were delivered at full term, and one was born at 36.5 weeks, and all were apparently healthy. Prenatal testing conducted on three of these six pregnancies showed normal results.
You can see the individual PGT results for the segmental aneuploids below. Also included are the prenatal testing results, if it was done, and any additional notes.
| Embryo Number | PGT-A Result | Outcome | Prenatal Testing | Additional Notes |
|---|---|---|---|---|
| 1 | del(7)(q11.21-qter) | Not pregnant | N/A | |
| 2 | del(12)(q21.33-qter) | Not pregnant | N/A | Transferred with a mosaic embryo |
| 3 | +4[mos], del(6)(q13-qter) | Not pregnant | N/A | |
| 4 | +8[mos], del(9)(q21.33-qter) and del(17)(pter-p11.2) | Not pregnant | N/A | |
| 5 | del(7)(pter-q11.22) and del(7)(q11.22-qter) | Biochemical pregnancy | N/A | Transferred with a mosaic embryo |
| 6 | del(7)(pter-p14.1) | Biochemical pregnancy | N/A | Transferred with a mosaic embryo |
| 7 | del(4)(pter-p15.1), dup(4)(p14-qter)[mos] | Biochemical pregnancy | N/A | |
| 8 | del(8)(pter-p21.3), del(11)(pter-q22.1)[mos], del(11)(q22.1-qter) | Spontaneous abortion (9 weeks) | N/A | Transferred with a mosaic embryo |
| 9 | del(7)(q21.2-qter) | Live birth | Amniocentesis; normal | Transferred with a euploid embryo, but baby was from segmental aneuploid due to sex |
| 10 | del(3)(pter-q22.3), del(10)(q25.1-qter), +19[mos] | Not pregnant | N/A | |
| 11 | Triple deletion/duplication complex | Not pregnant | N/A | |
| 12 | dup(2)(q24.2-qter) | Not pregnant | N/A | |
| 13 | dup(19)(q12-qter) | Not pregnant | N/A | Singleton pregnancy from a mosaic embryo only |
| 14 | dup(17)(q12-qter) | Biochemical pregnancy | N/A | Transferred with a mosaic embryo |
| 15 | dup(16)(p12.1-qter) | Spontaneous abortion | N/A | |
| 16 | +5[mos],dup(6)(q26-qter) | Live birth | Unknown | |
| 17 | +3[mos], +6[mos], +12[mos], +15[mos], dup(19)(q13.32-qter) | Live birth | None (declined) | |
| 18 | dup(13)(q14.12-qter)[mos], del(20)(pter-q13.12)[mos], dup(20)(q13.13-qter) | Live birth | cfDNA normal | |
| 19 | dup(4)(q13.1-qter) | Live birth | Amniocentesis karyotype with microarray; normal | |
| 20 | dup(5)(q33.2-q34), del(5)(q34-qter) | Not pregnant | N/A | |
| 21 | del(4)(q21.21-qter)[mos], dup(15)(pter-q25.2), del(15)(q26.1-qter) | Biochemical pregnancy | N/A | |
| 22 | del(10qter) | Not pregnant | N/A | |
| 23 | del(6qter) | Biochemical pregnancy | N/A | |
| 24 | del(1pter), dup(2qter) | Not pregnant | N/A | |
| 25 | del(2)(q35-qter) | Live birth | CVS karyotype with microarray; normal | Embryo was re-biopsied and tested via NGS; result was euploid |
The authors note that none of the segmental aneuploidies identified by PGT-A were found in the fetus or baby. They explain that the segmental aneuploidies detected are usually large enough that they might prevent the fetus from being viable. Babies born with segmental aneuploidies typically have abnormalities that involve only a smaller part of the chromosome. In a study by Levy et al. (2014), they performed a DNA analysis on miscarriage tissue, finding that only 1.6% of tissues had aneuploidies that were larger than 10 Mb (megabases, or 10 million base pairs — the unit of measurement for DNA). The average size of the segmental aneuploidies in the above 25 transfers was about 60 Mb.
Out of the 6 segmental aneuploids that did lead to a live birth, 4 were from duplications and 2 were from deletions. This suggests that duplications might be more likely to lead to a live birth than deletions, although the authors warn that the sample size is very low. A 2022 study showed that segmental aneuploids that were rebiopsied were more likely to be mosaic if they had a duplication compared to a deletion, so maybe this is the case afterall! You can read more about this in my post Segmental aneuploids: the main source for PGT-A false positives?
None of the embryos with multiple segmental aneuploidies resulted in a live birth, although many had mosaic abnormalities. This suggests that having more than a single segmental aneuploid may be detrimental, although the sample size is very low to be confident about this observation.
For those concerned that their specific segmental aneuploid isn’t listed in the table above, it’s important to note that there’s very little data on outcomes by specific chromosome. Even for mosaic embryos, current guidelines don’t prioritize which chromosome is affected, largely because outcomes are still uncertain. However, as more data becomes available, this could change. Read more in my Complete guide to mosaic embryos.
Besides the segmental aneuploids, what else did they report?
They actually transferred full aneuploid embryos! After transferring 30 aneuploid embryos (whole chromosome aneuploids), there was 1 ongoing pregnancy/live birth. This corresponds to a ongoing pregnancy/live birth rate of 3.3%. They didn’t provide any further information on this transfer. There was a statistical difference in ongoing pregnancy/live birth rate for whole chromosome aneuploids and segmental aneuploids (3.3% vs 24.0%, p= 0.022).
They also reported on the transfer of mosaic segmental aneuploids, with 126 of 244 transfers resulting in an ongoing pregnancy/live birth (51.6%). When they only considered high level mosaics (with >40% aneuploid cells), 44 out of 102 transfers resulted in an ongoing pregnancy/live birth (43.1%). Compared to the segmental aneuploid group, there was no statistically significant difference with the high level segmental mosaic group (24.0% vs 43.1%, p= 0.079). This suggests that high level segmental mosaics and segmental aneuploids have a similar live birth rate, at least based on the data from this study.
To my knowledge, there are only two studies that involved of the transfer of segmental aneuploids, both of which found successful ongoing pregnancies or live births (at 30.8%, based on one study). These studies also reported on whole chromosome aneuploid transfers, with only a single live birth. See my posts IVF outcomes following aneuploid embryo transfer and 144 “abnormal” (aneuploid/mosaic) embryos and their outcomes for more info.
The authors conclude that segmental aneuploid results need to be differentiated from whole chromosome aneuploid results to better understand their chances of success and help doctors and patients make informed decisions.
Reference
If you liked this post and want to support what I do, please consider a paid subscription, Patreon or donate through PayPal!
About Embryoman
Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.
Related posts:
Segmental aneuploids: the main source for PGT-A false positives?
Some embryos labeled as segmental aneuploid by PGT-A are actually euploid
IVF outcomes following aneuploid embryo transfer
144 “abnormal” (aneuploid/mosaic) embryos and their outcomes
PGDIS releases 2021 guidelines for mosaic embryo transfers
Does a PGT-A biopsy match the rest of the embryo?
ASRM’s 2024 committee opinion on the use of PGT-A
Chromosomal errors in IVF: What is aneuploidy and what causes it?