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Embryo Mosaicism: What You Need to Know

by Dr. Geoffrey Sher on June 28, 2017

In 2005, my associate Levent Keskintepe PhD and I introduced Preimplantation Genetic Screening (PGS) with the ability to identify all chromosomes in the embryo’s cells, into the field of IVF.

This approach, which is now widely used throughout the world, permits selection of those embryos that are most likely to be competent, and has dramatically improved IVF success rates.

However, some abnormal (or aneuploid) embryos are capable of autocorrecting and reverting to a normal karyotype (euploid) during intrauterine development and of then propagating healthy babies. This is because some embryos can harbor both aneuploid AND euploid cells. This combination of aneuploid plus euploid cells in the same embryo is referred to as “mosaicism.”

It is an indisputable fact that many mosaic embryos further cell replication can result in the euploid cell component predominating ultimately resulting in a healthy conceptus. In many cases it is not possible to identify embryo “mosaicism”. Accordingly, we tend to preserve certain aneuploid embryos and recommend that they be transferred.

Once pregnant chorionic villus sampling (CVS) or amniocentesis should be done to determine the normalcy of the pregnancy, providing the patient(s) with the opportunity to terminate such pregnancies if they so choose. Join me tomorrow at 1:00PM PST on my Facebook page, as I address the pros and cons of preserving versus discarding all aneuploid embryos and define my policy in advising such patients.

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  • Colleen - December 27, 2017 reply

    Hi Dr. Sher.
    I am 39 and after two egg retrieval’s all I have are two PGS abnormal embryos. I have good ovarian reserve but apparently poor egg quality. My physician has encouraged me to pursue using an egg donor. I’m not ready yet. I had 8 mature eggs, 7 fertilized and only one went to blast the first round. Second round, 12 mature eggs, 10 fertilized and only one went to blast. What protocol would you recommend for egg quality?
    I’m very curious about the PGS results..
    do you recommend retesting?
    Embryo #1. 47, XY +20
    Embryo #2. 44, XX -1,-9
    Would you consider transferring either of those?
    Any advice is welcome!! Thank you!

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - December 27, 2017 reply

    I would probably transfer embryo #1 as a possible mosaic.

    The potential for a woman’s eggs to undergo orderly development and maturation, while in large part being genetically determined can be profoundly influenced by the woman’s age, her “ovarian reserve” and proximity to menopause. It is also influenced by the protocol used for controlled ovarian stimulation (COH) which by fashioning the intra-ovarian hormonal environment, profoundly impacts egg development and maturation.
    After the menarche (age at which menstruation starts) a monthly process of repeatedly processing eggs continues until the menopause, by which time most eggs will have been used up, and ovulation and menstruation cease. When the number of eggs remaining in the ovaries falls below a certain threshold, ovarian function starts to wane over a 5 to10-years. This time period is referred to as the climacteric. With the onset of the climacteric, blood Follicle Stimulating Hormone (FSH) and later also Luteinizing Hormone (LH) levels begin to rise…. at first slowly and then more rapidly, ultimately culminating in the complete cessation of ovulation and menstruation (i.e. menopause).

    One of the early indications that the woman has entered the climacteric and that ovarian reserve is diminishing DOR) , is the detection of a basal blood FSH level above 9.0 MIU/ml and/ or an AMH level og <2.0ng/ml.
    Prior to the changes that immediately precede ovulation, virtually all human eggs have 23 pairs (i.e. 46) of chromosomes. Thirty six to forty hours prior to ovulation, a surge occurs in the release of LH by the pituitary gland. One of the main e purposes of this LH surge is to cause the chromosomes in the egg to divide n half (to 23 in number) in order that once fertilized by a mature sperm ends up having 23 chromosomes) the resulting embryo will be back to having 46 chromosomes. A “competent” mature egg is one that has precisely 23 chromosomes, not any more or any less. It is largely the egg, rather than the sperm that determines the chromosomal integrity of the embryo and only an embryo that has a normal component of 46 chromosomes (i.e. euploid) is “competent” to develop into a healthy baby. If for any reason the final number of chromosomes in the egg is less or more than 23 (aneuploid), it will be incapable of propagating a euploid, “competent” embryo. Thus egg/embryo aneuploidy (“incompetence”) is the leading cause of human reproductive dysfunction which can manifest as: arrested embryo development and/or failed implantation (which often presents as infertility), early miscarriage or chromosomal birth defects (e.g. Down’s syndrome). While most aneuploid (“incompetent”) embryos often fail to produce a pregnancy, some do. However, most such pregnancies miscarry early on. On relatively rare occasions, depending on the chromosome pair involved, aneuploid embryos can develop into chromosomally defective babies (e.g. Down’s syndrome).

    Up until a woman reaches her mid- thirties, at best, 1:2 of her eggs will likely be chromosomally normal. As she ages beyond her mid-thirties there will be a a progressive decline in egg quality such that by age 40 years only about 15%-20% of eggs are euploid and, by the time the woman reaches her mid-forties, less than 10% of her eggs are likely to be chromosomally normal. While most aneuploid embryos do appear to be microscopically abnormal under the light microscope, this is not invariably so. In fact, many aneuploid embryos a have a perfectly normal appearance under the microscope. This is why it is not possible to reliably differentiate between competent and incompetent embryos on the basis of their microscopic appearance (morphologic grade) alone.

    The process of natural selection usually precludes most aneuploid embryos from attaching to the uterine lining. Those that do attach usually do so for such only a brief period of time. In such cases the woman often will not even experience a postponement of menstruation. There will be a transient rise in blood hCG levels but in most cases the woman will be unaware of even having conceived (i.e. a “chemical pregnancy”). Alternatively, an aneuploid embryo might attach for a period of a few weeks before being expelled (i.e. a “miscarriage”). Sometimes (fortunately rarely) an aneuploid embryo will develop into a viable baby that is born with a chromosomal birth defect (e.g. Down’s syndrome).
    The fact that the incidence of embryo aneuploidy invariably increases with advancing age serves to explain why reproductive failure (“infertility”, miscarriages and birth defects), also increases as women get older.

    It is an over-simplification to represent that diminishing ovarian reserve as evidenced by raised FSH blood levels (and other tests) and reduced response to stimulation with fertility drugs is a direct cause of “poor egg/ embryo quality”. This common misconception stems from the fact that poor embryo quality (“incompetence”) often occurs in women who at the same time, because of the advent of the climacteric also have elevated basal blood FSH/LH levels and reduced AMH. But it is not the elevation in FSH or the low AMH that causes embryo “incompetence”. Rather it is the effect of advancing age (the “biological clock”) resulting a progressive increase in the incidence of egg aneuploidy, which is responsible for declining egg quality. Simply stated, as women get older “wear and tear” on their eggs increases the likelihood of egg and thus embryo aneuploidy. It just so happens that the two precipitating factors often go hand in hand.

    The importance of the IVF stimulation protocol on egg/embryo quality cannot be overstated. This factor seems often to be overlooked or discounted by those IVF practitioners who use a “one-size-fits-all” approach to ovarian stimulation. My experience is that the use of individualized/customized COS protocols can greatly improve IVF outcome in patients at risk – particularly those with diminished ovarian reserve (“poor responders”) and those who are “high responders” (women with PCOS , those with dysfunctional or absent ovulation, and young women under 25 years of age).
    While no one can influence underlying genetics or turn back the clock on a woman’s age, any competent IVF specialist should be able to tailor the protocol for COS to meet the individual needs of the patient.
    During the normal ovulation cycle, ovarian hormonal changes are regulated to avoid irregularities in production and interaction that could adversely influence follicle development and egg quality. As an example, small amounts of androgens (male hormones such as testosterone) that are produced by the ovarian stroma (the tissue surrounding ovarian follicles) during the pre-ovulatory phase of the cycle enhance late follicle development, estrogen production by the granulosa cells (cells that line the inner walls of follicles), and egg maturation.
    However, over-production of testosterone can adversely influence the same processes. It follows that protocols for controlled ovarian stimulation (COS should be geared toward optimizing follicle growth and development (without placing the woman at risk from overstimulation), while at the same time avoiding excessive ovarian androgen production. Achievement of such objectives requires a very individualized approach to choosing the protocol for COS with fertility drugs as well as the precise timing of the “trigger shot” of hCG.

    It is important to recognize that the pituitary gonadotropins, LH and FSH, while both playing a pivotal role in follicle development, have different primary sites of action in the ovary. The action of FSH is mainly directed towards the cells lining the inside of the follicle that are responsible for estrogen production. LH, on the other hand, acts primarily on the ovarian stroma to produce male hormones/ androgens (e.g. androstenedione and testosterone). A small amount of testosterone is necessary for optimal estrogen production. Over-production of such androgens can have a deleterious effect on granulosa cell activity, follicle growth/development, egg maturation, fertilization potential and subsequent embryo quality. Furthermore, excessive ovarian androgens can also compromise estrogen-induced endometrial growth and development.

    In conditions such as polycystic ovarian syndrome (PCOS), which is characterized by increased blood LH levels, there is also increased ovarian androgen production. It is therefore not surprising that “poor egg/embryo quality” is often a feature of this condition. The use of LH-containing preparations such as Menopur further aggravates this effect. Thus we recommend using FSH-dominant products such as Follistim, Puregon, and Gonal-F in such cases. While it would seem prudent to limit LH exposure in all cases of COS, this appears to be more vital in older women, who tend to be more sensitive to LH

    It is common practice to administer gonadotropin releasing hormone agonists (GnRHa) agonists such as Lupron, and, GnRH-antagonists such as Ganirelix and Orgalutron to prevent the release of LH during COS. GnRH agonists exert their LH-lowering effect over a number of days. They act by causing an initial outpouring followed by a depletion of pituitary gonadotropins. This results in the LH level falling to low concentrations, within 4-7 days, thereby establishing a relatively “LH-free environment”. GnRH Antagonists, on the other hand, act very rapidly (within a few hours) to block pituitary LH release, so as achieve the same effect.

    Long Agonist (Lupron/Buserelin) Protocols: The most commonly prescribed protocol for Lupron/gonadotropin administration is the so-called “long protocol”. Here, Lupron is given, starting a week or so prior to menstruation. This results in an initial rise in FSH and LH level, which is rapidly followed by a precipitous fall to near zero. It is followed by uterine withdrawal bleeding (menstruation), whereupon gonadotropin treatment is initiated while daily Lupron injections continue, to ensure a “low LH” environment. A modification to the long protocol which I prefer using in cases of DOR, is the Agonist/Antagonist Conversion Protocol (A/ACP) where, upon the onset of a Lupron-induced bleed , this agonist is supplanted by an antagonist (Ganirelix/Cetrotide/Orgalutron) and this is continued until the hCG trigger. In many such cases I supplement with human growth hormone (HGH) to try and further enhance response and egg development.

    Lupron Flare/Micro-Flare Protocol: Another approach to COS is by way of so-called “(micro) flare protocols”. This involves initiating gonadotropin therapy simultaneous with the administration of GnRH agonist (e.g. Lupron/Buserelin). The intent here is to deliberately allow Lupron to elicit an initial surge (“flare”) in pituitary FSH release in order to augment FSH administration by increased FSH production. Unfortunately, this “spring board effect” represents “a double edged sword” because while it indeed increases the release of FSH, it at the same time causes a surge in LH release. The latter can evoke excessive ovarian stromal androgen production which could potentially compromise egg quality, especially in older women and women with PCOS, whose ovaries have increased sensitivity to LH. I am of the opinion that by evoking an exaggerated ovarian androgen response, such “(micro) flare protocols” can harm egg/embryo quality and reduce IVF success rates, especially in older women, and in women with diminished ovarian reserve. Accordingly, I do not prescribe them at all.

    Estrogen Priming – My approach for “Poor Responders” Our patients who have demonstrated reduced ovarian response to COS as well as those who by way of significantly raised FSH blood levels are likely to be “poor responders”, are treated using a “modified” long protocol. The approach involves the initial administration of GnRH agonist for a number of days to cause pituitary down-regulation. Upon menstruation and confirmation by ultrasound and measurement of blood estradiol levels that adequate ovarian suppression has been achieved, the dosage of GnRH agonist is drastically lowered and the woman is given twice-weekly injections of estradiol for a period of 8. COS is thereupon initiated using a relatively high dosage of FSH-(Follistim, Bravelle, Puregon or Gonal F) which is continued along with daily administration of GnRH agonist until the “hCG trigger.” By this approach we have been able to significantly improve ovarian response to gonadotropins in many of hitherto “resistant patients”.
    The “Trigger”: hCG (Profasi/Pregnyl/Novarel) versus Lupron: With ovulation induction using fertility drugs, the administration of 10,000U hCGu (the hCG “trigger”) mimics the LH surge, sending the eggs (which up to that point are immature (M1) and have 46 chromosomes) into maturational division (meiosis) This process is designed to halve the chromosome number , resulting in mature eggs (M2) that will have 23 chromosomes rather that the 46 chromosomes it had prior to the “trigger”. Such a chromosomally normal, M2 egg, upon being fertilized by mature sperm (that following maturational division also has 23 chromosomes) will hopefully propagate embryos that have 46 chromosomes and will be “:competent” to propagate viable pregnancies. The key is to trigger with no less than 10,000U of hCGu (Profasi/Novarel/Pregnyl) and if hCGr (Ovidrel) is used, to make sure that 500mcg (rather than 250mcg) is administered. In my opinion, any lesser dosage will reduce the efficiency of meiosis, and increase the risk of the eggs being chromosomally abnormal. . I also do not use the agonist (Lupron) “trigger”. This approach which is often recommended for women at risk of overstimulation, is intended to reduce the risk of OHSS. The reason for using the Lupron trigger is that by inducing a surge in the release of LH by the pituitary gland it reduces the risk of OHSS. This is true, but this comes at the expense of egg quality because the extent of the induced LH surge varies and if too little LH is released, meiosis can be compromised, thereby increasing the percentage of chromosomally abnormal and of immature (M1) eggs. The use of “coasting” in such cases (see below) can obviate this effect.

    Severe Ovarian Hyperstimulation Syndrome (OHSS): Women with certain types of absent or dysfunctional ovulation as well as those who have polycystic ovarian syndrome (PCOS) are highly sensitive to gonadotropins and are at risk of developing OHSS. Such women are also more likely than others to produce poor quality eggs/embryos which, they are often led to believe is attributable to an intrinsic egg defect that is characteristic of their PCOS condition. This is not necessarily so. The most likely reason as to why many women with PCOS develop an excessive number of follicles and then go on to produce poor quality eggs/embryos has to do with the fact that, in an attempt to contain reduce the risk of OHSS they are often administered hCG prematurely – prior to the attainment of optimal egg maturation.

    “Prolonged Coasting”: In the early nineties, we introduced “Prolonged Coasting”, a procedure which eliminates the risk of OHSS while allowing the hCG trigger to be deferred for long enough as to allow for optimal follicle/egg maturation to take place. Coasting involves withholding gonadotropin therapy while the administration of GnRH agonist/antagonist is continued. The daily measurement of blood estradiol is continued until the concentration drops below a safe threshold level, at which time HCG is administered (regardless of the number of follicles). When appropriately implemented “coasting” results in the production of good quality eggs/embryos, in circumstances where this might otherwise not have been possible.

    If you are interested in my advice or medical services, I urge you to contact my concierge, Julie Dahan ASAP to set up a Skype or an in-person consultation with me. You can also contact Julie by phone or via email at 702-533-2691/ Julied@sherivf.com. You can also apply online at http://www.SherIVF.com.
    Also, my book, “In Vitro Fertilization, the ART of Making Babies” is available as a down-load through http://www.Amazon.com or from most bookstores and public libraries.

    Geoffrey Sher MD

  • Rachel - November 17, 2017 reply

    Would love your thoughts! I am 39 and just completed my 2nd IVF cycle. The first round was 6 months ago, where we ended up with 3 abnormal embryos 48/+14/+15/+21/-22 , 45/-13 and 46/dup(6)(q22q27). My doctor said the first one (48/+14/+15/+21/-22) would be the only one he would be willing to transfer since it was mosaic. We decided to pass and just completed another round (lupron flare this time) where we are waiting on results from 2 day-5 blastocysts. I am of course hoping for better results this time but I cant help to wonder about our mosaic from round 1.

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - November 17, 2017 reply

    Very respectfully Rachel, I disagree with your Doctor. There is no way to know with cofidence whether an embryo is “mosaic”. However, the ones that are most likely to be so are the ones with autosomal single chromosome defects. So in your case, I think #2 with a -13 monosomy is the best to try and #3 possibly also.

    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. “autocorrection”) 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 , 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 aneuploid embryos the possibility exists that we could 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 “autocorrection” 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.” As stated, some 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 “autocorrection”. 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 considerable clinical value. And would provide a strong argument in favor of preserving certain aneuploid embryos for future dispensation.
    Aneuploidy, involves the addition (trisomy) or subtraction (monosomy) of one chromosome in a given pair. As previously stated, some aneuploidies are meiotic in origin while others are mitotic “mosaics”. Certain aneuploidies involve only a single, chromosome pair (simple aneuploidy) while others involve more than a single pair (i.e. complex aneuploidy). Aside from monosomy involving absence of the y-sex chromosome (i.e. XO) which can resulting in a live birth (Turner syndrome) all monosomies involving autosomes (non-sex chromosomes) are lethal and will not result in viable offspring). Some autosomal meiotic aneuploidies, especially trisomies 13, 18, 21, can progress to viable, but severely chromosomally defective babies. All other meiotic autosomal trisomies will almost invariably, either not attach to the uterine lining or upon attachment, will soon be rejected. All forms of meiotic aneuploidy are irreversible while mitotic aneuploidy (“mosaicism) often autocorrects in the uterus. Most complex aneuploidies are meiotic in origin and will almost invariably fail to propagate viable pregnancies.
    There is presently no microscopic or genetic test that can reliable differentiate between meiotic and mitotic aneuploidy. Notwithstanding this, the fact that some “mosaic” embryos can autocorrect in the uterus, makes a strong argument in favor of transferring aneuploid of embryos in the hope that the one(s) transferred might be “mosaic” and might propagate viable healthy pregnancies. On the other hand, it is the fear that embryo aneuploidy might result in a chromosomally abnormal baby that has led many IVF physicians to strongly oppose the transfer of any aneuploid embryos to the uterus.
    While certain meiotic aneuploid trisomies (e.g. trisomies 13, 18, & 21) can and sometimes do result in chromosomally defective babies, no other meiotic autosomal trisomies can do so. Thus the transfer of trisomic embryos in the hope that one or more might be mosaic, should exclude the use of embryos with trisomies 13, 18 or 21. Conversely, no autosomal monosomic embryos are believed to be capable of resulting in viable pregnancies, thereby making the transfer of autosomally monosomic embryos, in the hope that they are “mosaic”, a far less risky proposition. Needless to say, if such action is being contemplated, it is absolutely essential to make full disclosure to the patient (s) , and to insure the completion of a detailed informed consent agreement which would include a commitment by the patient (s) 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.

    Geoff Sher

  • Nadege Montagnon - October 31, 2017 reply

    Dear Doctor,
    I am 41 years old.
    We did 2 rounds of IVF, each time with PGS.
    3 blastocysts were tested.
    The PGS results were the following:
    – Abnormal: +7, +21
    – Abnormal: -13
    -Abnormal: -19
    Do you think that these embryos have a chance to be mosaic and would have the possibility to autocorrect themselves? Would you do a transfer of such embryos?
    Our doctor told us that they were abnormal and that there would not be any transfer.
    Thank you in advance for your response.
    Ps: sorry for my English, but I am French.

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - October 31, 2017 reply

    Yes! The -13 and -19 could be mosaic.

    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 preimplantation embryo development, and represents a major cause of early pregnancy loss. About a decade ago, I and an associate, Levent Keskintepe PhD 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. “autocorrection”) 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 , 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 aneuploid embryos the possibility exists that we could 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 “autocorrection” 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.” As stated, some 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 “autocorrection”. 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 considerable clinical value. And would provide a strong argument in favor of preserving certain aneuploid embryos for future dispensation.
    Aneuploidy, involves the addition (trisomy) or subtraction (monosomy) of one chromosome in a given pair. As previously stated, some aneuploidies are meiotic in origin while others are mitotic “mosaics”. Certain aneuploidies involve only a single, chromosome pair (simple aneuploidy) while others involve more than a single pair (i.e. complex aneuploidy). Aside from monosomy involving absence of the y-sex chromosome (i.e. XO) which can resulting in a live birth (Turner syndrome) all monosomies involving autosomes (non-sex chromosomes) are lethal and will not result in viable offspring). Some autosomal meiotic aneuploidies, especially trisomies 13, 18, 21, can progress to viable, but severely chromosomally defective babies. All other meiotic autosomal trisomies will almost invariably, either not attach to the uterine lining or upon attachment, will soon be rejected. All forms of meiotic aneuploidy are irreversible while mitotic aneuploidy (“mosaicism) often autocorrects in the uterus. Most complex aneuploidies are meiotic in origin and will almost invariably fail to propagate viable pregnancies.
    There is presently no practical test that can reliable differentiate between meiotic and mitotic aneuploidy. Notwithstanding this, the fact that some “mosaic” embryos can autocorrect in the uterus, makes a strong argument in favor of transferring aneuploid of embryos in the hope that the one(s) transferred might be “mosaic” and might propagate viable healthy pregnancies. On the other hand, it is the fear that embryo aneuploidy might result in a chromosomally abnormal baby that has led many IVF physicians to strongly oppose the transfer of aneuploid embryos to the uterus.
    Certain meiotic aneuploid trisomy embryos (e.g. trisomies 13, 18, & 21) can and sometimes do, result in aneuploid concepti. Thus, in my opinion, unless the woman/couple receiving such embryos is willing to commit to terminating a resulting pregnancy found through amniocentesis or chorionic villus sampling (CVS) to be so affected, she/they are probably best advised not to transfer such embryos. Other autosomal trisomy embryos will hardly ever produce viable euploid concepti and can thus, in my opinion be transferred in the hope that auto correction will occur in-utero. However, in all cases, and amniocentesis or CVS should be performed to make certain that the baby is euploid. Conversely, no autosomal monosomy embryos are believed to be capable of resulting in viable pregnancies, thereby making the transfer of autosomal monosomy embryos, in the hope that they are “mosaic”, a far less risky proposition. Needless to say, if such action is being contemplated in any such cases, it is absolutely essential to make full disclosure to the patient (s) , and to insure the completion of a detailed informed consent agreement which would include a commitment by the patient (s) to undergo prenatal genetic testing (amniocentesis/CVS) 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.

    Geoff Sher

    Nadege Montagnon - November 1, 2017 reply

    Thank you so much for your response Dr. Sher.

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - November 1, 2017 reply

    You are very welcome.

    Geoff Sher

  • Justyna Akyondem - September 14, 2017 reply

    Dr. Sher:

    Thank you so much for posting this video and article. This is incredibly helpful!

    Are there specific questions that I would need to ask my lab in order to get a good report of the PGS results? I have found that detailed information is given only when asked for.

    Also what are your thoughts about the accuracy of a single 6-10 cell Trophoderm biopsy on a day 5 blastocyst. I have read a number of papers suggesting that such a small biopsy sample size is not adequate to accurately identify the existence of multiple cell lines in a day 5 blastocyst.

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - September 15, 2017 reply

    Just asked for a comprehensive report…That should do it. I think the 6-10 cell biopsy is adequate.

    Geoff Sher

  • Chrissy - July 31, 2017 reply

    What are you thoughts on transferring a monosomy 20 embryo? The first time it was tested it came back as “no result” so the clinic did a re-biopsy and sent back in and it came back with the above abnormality. Would you say it’s likely too abnormal?

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - July 31, 2017 reply

    I would do the transfer. It could be a mosaic.

    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. “autocorrection”) 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 , 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 aneuploid embryos the possibility exists that we could 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 “autocorrection” 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.” As stated, some 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 “autocorrection”. 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 considerable clinical value. And would provide a strong argument in favor of preserving certain aneuploid embryos for future dispensation.
    Aneuploidy, involves the addition (trisomy) or subtraction (monosomy) of one chromosome in a given pair. As previously stated, some aneuploidies are meiotic in origin while others are mitotic “mosaics”. Certain aneuploidies involve only a single, chromosome pair (simple aneuploidy) while others involve more than a single pair (i.e. complex aneuploidy). Aside from monosomy involving absence of the y-sex chromosome (i.e. XO) which can resulting in a live birth (Turner syndrome) all monosomies involving autosomes (non-sex chromosomes) are lethal and will not result in viable offspring). Some autosomal meiotic aneuploidies, especially trisomies 13, 18, 21, can progress to viable, but severely chromosomally defective babies. All other meiotic autosomal trisomies will almost invariably, either not attach to the uterine lining or upon attachment, will soon be rejected. All forms of meiotic aneuploidy are irreversible while mitotic aneuploidy (“mosaicism) often autocorrects in the uterus. Most complex aneuploidies are meiotic in origin and will almost invariably fail to propagate viable pregnancies.
    There is presently no microscopic or genetic test that can reliable differentiate between meiotic and mitotic aneuploidy. Notwithstanding this, the fact that some “mosaic” embryos can autocorrect in the uterus, makes a strong argument in favor of transferring aneuploid of embryos in the hope that the one(s) transferred might be “mosaic” and might propagate viable healthy pregnancies. On the other hand, it is the fear that embryo aneuploidy might result in a chromosomally abnormal baby that has led many IVF physicians to strongly oppose the transfer of any aneuploid embryos to the uterus.
    While certain meiotic aneuploid trisomies (e.g. trisomies 13, 18, & 21) can and sometimes do result in chromosomally defective babies, no other meiotic autosomal trisomies can do so. Thus the transfer of trisomic embryos in the hope that one or more might be mosaic, should exclude the use of embryos with trisomies 13, 18 or 21. Conversely, no autosomal monosomic embryos are believed to be capable of resulting in viable pregnancies, thereby making the transfer of autosomally monosomic embryos, in the hope that they are “mosaic”, a far less risky proposition. Needless to say, if such action is being contemplated, it is absolutely essential to make full disclosure to the patient (s) , and to insure the completion of a detailed informed consent agreement which would include a commitment by the patient (s) 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.

    Geoff Sher

  • Brianna - June 29, 2017 reply

    What are your thoughts/opinions on transferring an XXY or an XYY embryo? Thanks!

    Dr. Geoffrey Sher

    Dr. Geoffrey Sher - June 29, 2017 reply

    I would not knowingly do so!

    Geoff Sher

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