Ask Our Doctors – Archive
Our Medical Directors are outstanding physicians that you will find to be very personable and compassionate, who take care to ensure that you have the most cutting-edge fertility treatments at your disposal. This is your outlet to ask your questions to the doctors.
Thank you for your discussion about mosaic embryos.
We had NGS testing done on our 2 remaining frozen embryos from donor egg. Both are grade 3 (fair/poor) and were hatching at thaw. The first one tested euploid and is recommended for transfer. The second one tested 47, xx, 20, high level mosaic (the scale being high level is >40-80% mosaic.) Our Dr. does not recommend transferring the 2nd one as she is high level mosaic.
Does this recommendation align with your findings on mosaics, as she is high level mosaic?
Thank you so much.
Very respectfully Judy. I disagree. I would transfer both and follow-up with CVS/amniocentesis if you do conceive.
Good luck!
Geoff Sher
Hi Dr Sher would you transfer an embryo that is complex aneuploid & mosaic chromosomes: with these results? 47; mos -12, 21, 22 mos del (X) (p22.2 -pter)
if its a maybe what would be the consideration?
Thanks so much for what you do Dr Sher!
I would not recommend transferring such an embryo.
Human embryo development occurs through a process that encompasses reprogramming, sequential cleavage divisions and mitotic chromosome segregation and embryonic genome activation. Chromosomal abnormalities may arise during germ cell and/or pre-implantation embryo development, and represents a major cause of early pregnancy loss. About a decade ago, I and an associate, Levent Keskintepe Ph.D. were the first to introduce full embryo karyotyping (identification of all 46 chromosomes) through preimplantation genetic sampling (PGS) as a method by which to selectively transfer only euploid embryos (i.e. those that have a full component of chromosomes) to the uterus. We subsequently reported on a 2-3 fold improvement in implantation and birth rates as well as a significant reduction in early pregnancy loss, following IVF. Since then PGS has grown dramatically in popularity such that it is now widely used throughout the world.
Most IVF programs that offer PGS services, require that all participating patients consent to all their aneuploid embryos (i.e. those with an irregular quota of chromosomes) be disposed of. However, there is now growing evidence to suggest that following embryo transfer, some aneuploid embryos will in the process of ongoing development, convert to the euploid state (i.e. “auto correction”) and then go on to develop into chromosomally normal offspring. In fact, I am personally aware of several such cases occurring within our IVF network. So clearly, by summarily discarding all aneuploid embryos as a matter of routine we are sometimes destroying some embryos that might otherwise have “autocorrected” and gone on to develop into normal offspring.
Thus by discarding all aneuploid embryos we, in so doing, might be denying some women the opportunity of having a baby. This creates a major ethical and moral dilemma for those of us that provide the option of PGS to our patients. On the one hand, we strive “to avoid knowingly doing harm” (the Hippocratic Oath) and as such would prefer to avoid or minimize the risk of miscarriage and/or chromosomal birth defects and on the other hand we would not wish to deny patients with aneuploid embryos, the opportunity to have a baby.
The basis for such embryo “auto correction” lies in the fact that some embryos found through PGS-karyotyping to harbor one or more aneuploid cells (blastomeres) will often also harbor chromosomally normal (euploid) cells (blastomeres). The coexistence of both aneuploid and euploid cells coexisting in the same embryo is referred to as “mosaicism.” Many such mosaic embryos will In the process of subsequent cell replication convert to the normal euploid state (i.e. autocorrect)
It is against this background, that an ever increasing number of IVF practitioners, rather than summarily discard PGS-identified aneuploid embryos are now choosing to cryobanking (freeze-store) certain of them, to leave open the possibility of ultimately transferring them to the uterus. In order to best understand the complexity of the factors involved in such decision making, it is essential to understand the causes of embryo aneuploidy of which there are two varieties:
1.Meiotic aneuploidy” results from aberrations in chromosomal numerical configuration that originate in either the egg (most commonly) and/or in sperm, during preconceptual maturational division (meiosis). Since meiosis occurs in the pre-fertilized egg or in and sperm, it follows that when aneuploidy occurs due to defective meiosis, all subsequent cells in the developing embryo/blastocyst/conceptus inevitably will be aneuploid, precluding subsequent “auto correction”. Meiotic aneuploidy will thus invariably be perpetuated in all the cells of the embryo as they replicate. It is a permanent phenomenon and is irreversible. All embryos so affected are thus fatally damaged. Most will fail to implant and those that do implant will either be lost in early pregnancy or develop into chromosomally defective offspring (e.g. Down syndrome, Edward syndrome, Turner syndrome).
2.“Mitotic aneuploidy” occurs when following fertilization and subsequent cell replication (cleavage), some cells (blastomeres) of a meiotically euploid early embryo mutate and become aneuploid. This is referred to as mosaicism. Thereupon, with continued subsequent cell replication (mitosis) the chromosomal make-up (karyotype) of the embryo might either comprise of predominantly aneuploid cells or euploid cells. The subsequent viability or competency of the conceptus will thereupon depend on whether euploid or aneuploid cells predominate. If in such mosaic embryos aneuploid cells predominate, the embryo will be “incompetent”). If (as is frequently the case) euploid cells prevail, the mosaic embryo will be “competent” and capable of propagating a normal conceptus.
Since some mitotically aneuploid (“mosaic”) embryos can and indeed do “autocorrect’ while meiotically aneuploid embryos cannot, it follows that an ability to differentiate between these two varieties of aneuploidy would be of enormous clinical value. Since some mosaic embryos can “autocorrect” and even go on to propagate a viable baby, the ability to confirm that aneuploidy is mitotic (potentially reversible) would provide a strong argument in favor of preserving certain aneuploid embryos for future dispensation. Unfortunately however, there is presently no microscopic or genetic test that can reliable differentiate between meiotic and mitotic aneuploidy.
Aneuploidy, whether meiotic or mitotic in origin involves the addition of one or more chromosomes to a given pair in human embryos. Certain aneuploidies involve only a single, chromosome pair (simple aneuploidy) while others involve more than a single pair (i.e. complex aneuploidy). Evidence suggests that complex aneuploidy, whether meiotic or mitotic in origin is almost always lethal while all forms of meiotic aneuploidy are permanent. Some aneuploidies, especially those that involve addition of a chromosome to any pair (trisomy) will at times progress to clinical pregnancies (e.g. trisomy 15, 18, 21 or when the sex chromosomes are involve). And as stated previously, most aneuploid embryos, should they attach, will miscarry or result in a chromosomally defective offspring.
On the other hand, some aneuploid embryos have one chromosome (in a given pair) missing (i.e. monosomy). Aside from monosomy involving absence of the Y-sex chromosome (i.e. XO) which can resulting in a live birth (Turner syndrome) all other monosomies involving autosomes (non-sex chromosomes) are lethal and will not result in viable offspring.
Since it is presently not possible, without removing more than 1 cell from an embryo (a very traumatic event) to differentiate between meiotic and mitotic aneuploidy, it follows that making a diagnosis of embryo aneuploidy does not allow for identification of mosaic embryos for transfer. This is especially true when it comes to trisomic embryos that can and sometimes do, propagate chromosomal birth defects such as Down syndrome. It is important to bear in mind that the transfer of trisomic embryos (whether due to meiotic or mitotic aneuploidy) can result in miscarriage or a birth defect. This makes any attempt to transfer such embryos to the uterus fraught with risk and in my opinion, ill advised. Conversely, since true meiotic autosomal monosomic embryos cannot propagate viable pregnancies, performing embryo transfer in such cases in the hope that the aneuploidy is mitotic (mosaic) in origin and will spontaneously “ auto correct”, is a rational consideration. Needless to say, such action would require full disclosure, and the execution of a detailed, informed consent agreement which would include an expressed commitment to undergo prenatal genetic testing aimed at excluding a chromosomal defect in the developing baby and/or a willingness to terminate the pregnancy should a serious birth defect be diagnosed.
Since it is meiotic rather than mitotic aneuploidy that is invariably lethal and given that meiotic aneuploidy originates in the egg, it is my belief that the closer to fertilization that embryo biopsy is done for PGS, the more likely it is that any aneuploidy detected, will be meiotic in origin. The longer you wait thereafter, the greater the likelihood that with repeated mitotic division, mutational changes will result in mitotic aneuploidy (mosaicism). This is why I strongly believe embryo biopsies should be performed on day 2-3 post fertilization rather on day 5-6 days (the blastocyst stage).”
Geoff Sher
800-780-7437
Hi Dr Sher,
I’m devastated to hear from my Dr that my pregnancy is not looking viable. My hcg numbers continue to double however my sac has barely grown. On 11/2 it measure 5w 4 d and on 11/7 it measured 5w 6d and the Dr. said it should be 6w 2d. Is there any hope here at all for this to grow at my next visit or is all lost?
We had 8 time ivf process unsucces the problem is the womens eggs are empty Any treatment for this ?During the ivf process everything goes right but at the egg retrival all egss 12 or 13 are empty :(:(
Dr Sher
I have an embryo 4AA that has tested trisomy 7 on NGS PGS. We are hoping it is an undiagnosed mosaic. Would you consider transferring this as a last option? Have you seen any successes from non-mosaic abnormal embryo transfers? Do you think the fact that it is trisomy 7, which can be found in placental biopsies/CVS with normal babies in natural pregnancies has any significance ?
thank you
I would definitely transfer it!
Human embryo development occurs through a process that encompasses reprogramming, sequential cleavage divisions and mitotic chromosome segregation and embryonic genome activation. Chromosomal abnormalities may arise during germ cell and/or pre-implantation embryo development, and represents a major cause of early pregnancy loss. About a decade ago, I and an associate, Levent Keskintepe Ph.D. were the first to introduce full embryo karyotyping (identification of all 46 chromosomes) through preimplantation genetic sampling (PGS) as a method by which to selectively transfer only euploid embryos (i.e. those that have a full component of chromosomes) to the uterus. We subsequently reported on a 2-3 fold improvement in implantation and birth rates as well as a significant reduction in early pregnancy loss, following IVF. Since then PGS has grown dramatically in popularity such that it is now widely used throughout the world.
Most IVF programs that offer PGS services, require that all participating patients consent to all their aneuploid embryos (i.e. those with an irregular quota of chromosomes) be disposed of. However, there is now growing evidence to suggest that following embryo transfer, some aneuploid embryos will in the process of ongoing development, convert to the euploid state (i.e. “auto correction”) and then go on to develop into chromosomally normal offspring. In fact, I am personally aware of several such cases occurring within our IVF network. So clearly, by summarily discarding all aneuploid embryos as a matter of routine we are sometimes destroying some embryos that might otherwise have “autocorrected” and gone on to develop into normal offspring.
Thus by discarding all aneuploid embryos we, in so doing, might be denying some women the opportunity of having a baby. This creates a major ethical and moral dilemma for those of us that provide the option of PGS to our patients. On the one hand, we strive “to avoid knowingly doing harm” (the Hippocratic Oath) and as such would prefer to avoid or minimize the risk of miscarriage and/or chromosomal birth defects and on the other hand we would not wish to deny patients with aneuploid embryos, the opportunity to have a baby.
The basis for such embryo “auto correction” lies in the fact that some embryos found through PGS-karyotyping to harbor one or more aneuploid cells (blastomeres) will often also harbor chromosomally normal (euploid) cells (blastomeres). The coexistence of both aneuploid and euploid cells coexisting in the same embryo is referred to as “mosaicism.” Many such mosaic embryos will In the process of subsequent cell replication convert to the normal euploid state (i.e. autocorrect)
It is against this background, that an ever increasing number of IVF practitioners, rather than summarily discard PGS-identified aneuploid embryos are now choosing to cryobanking (freeze-store) certain of them, to leave open the possibility of ultimately transferring them to the uterus. In order to best understand the complexity of the factors involved in such decision making, it is essential to understand the causes of embryo aneuploidy of which there are two varieties:
1.Meiotic aneuploidy” results from aberrations in chromosomal numerical configuration that originate in either the egg (most commonly) and/or in sperm, during preconceptual maturational division (meiosis). Since meiosis occurs in the pre-fertilized egg or in and sperm, it follows that when aneuploidy occurs due to defective meiosis, all subsequent cells in the developing embryo/blastocyst/conceptus inevitably will be aneuploid, precluding subsequent “auto correction”. Meiotic aneuploidy will thus invariably be perpetuated in all the cells of the embryo as they replicate. It is a permanent phenomenon and is irreversible. All embryos so affected are thus fatally damaged. Most will fail to implant and those that do implant will either be lost in early pregnancy or develop into chromosomally defective offspring (e.g. Down syndrome, Edward syndrome, Turner syndrome).
2.“Mitotic aneuploidy” occurs when following fertilization and subsequent cell replication (cleavage), some cells (blastomeres) of a meiotically euploid early embryo mutate and become aneuploid. This is referred to as mosaicism. Thereupon, with continued subsequent cell replication (mitosis) the chromosomal make-up (karyotype) of the embryo might either comprise of predominantly aneuploid cells or euploid cells. The subsequent viability or competency of the conceptus will thereupon depend on whether euploid or aneuploid cells predominate. If in such mosaic embryos aneuploid cells predominate, the embryo will be “incompetent”). If (as is frequently the case) euploid cells prevail, the mosaic embryo will be “competent” and capable of propagating a normal conceptus.
Since some mitotically aneuploid (“mosaic”) embryos can and indeed do “autocorrect’ while meiotically aneuploid embryos cannot, it follows that an ability to differentiate between these two varieties of aneuploidy would be of enormous clinical value. Since some mosaic embryos can “autocorrect” and even go on to propagate a viable baby, the ability to confirm that aneuploidy is mitotic (potentially reversible) would provide a strong argument in favor of preserving certain aneuploid embryos for future dispensation. Unfortunately however, there is presently no microscopic or genetic test that can reliable differentiate between meiotic and mitotic aneuploidy.
Aneuploidy, whether meiotic or mitotic in origin involves the addition of one or more chromosomes to a given pair in human embryos. Certain aneuploidies involve only a single, chromosome pair (simple aneuploidy) while others involve more than a single pair (i.e. complex aneuploidy). Evidence suggests that complex aneuploidy, whether meiotic or mitotic in origin is almost always lethal while all forms of meiotic aneuploidy are permanent. Some aneuploidies, especially those that involve addition of a chromosome to any pair (trisomy) will at times progress to clinical pregnancies (e.g. trisomy 15, 18, 21 or when the sex chromosomes are involve). And as stated previously, most aneuploid embryos, should they attach, will miscarry or result in a chromosomally defective offspring.
On the other hand, some aneuploid embryos have one chromosome (in a given pair) missing (i.e. monosomy). Aside from monosomy involving absence of the Y-sex chromosome (i.e. XO) which can resulting in a live birth (Turner syndrome) all other monosomies involving autosomes (non-sex chromosomes) are lethal and will not result in viable offspring.
Since it is presently not possible, without removing more than 1 cell from an embryo (a very traumatic event) to differentiate between meiotic and mitotic aneuploidy, it follows that making a diagnosis of embryo aneuploidy does not allow for identification of mosaic embryos for transfer. This is especially true when it comes to trisomic embryos that can and sometimes do, propagate chromosomal birth defects such as Down syndrome. It is important to bear in mind that the transfer of trisomic embryos (whether due to meiotic or mitotic aneuploidy) can result in miscarriage or a birth defect. This makes any attempt to transfer such embryos to the uterus fraught with risk and in my opinion, ill advised. Conversely, since true meiotic autosomal monosomic embryos cannot propagate viable pregnancies, performing embryo transfer in such cases in the hope that the aneuploidy is mitotic (mosaic) in origin and will spontaneously “ auto correct”, is a rational consideration. Needless to say, such action would require full disclosure, and the execution of a detailed, informed consent agreement which would include an expressed commitment to undergo prenatal genetic testing aimed at excluding a chromosomal defect in the developing baby and/or a willingness to terminate the pregnancy should a serious birth defect be diagnosed.
Since it is meiotic rather than mitotic aneuploidy that is invariably lethal and given that meiotic aneuploidy originates in the egg, it is my belief that the closer to fertilization that embryo biopsy is done for PGS, the more likely it is that any aneuploidy detected, will be meiotic in origin. The longer you wait thereafter, the greater the likelihood that with repeated mitotic division, mutational changes will result in mitotic aneuploidy (mosaicism). This is why I strongly believe embryo biopsies should be performed on day 2-3 post fertilization rather on day 5-6 days (the blastocyst stage).”
Geoff Sher