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.
Hello,
I’m 33 years old and have two healthy children conceived naturally with my husband. We are undergoing IVF to avoid a genetic condition my husband and I both are recessive carriers of – connexin26. Had full pre-ivf work up done and no abnormalities. First three cycles were failures (last resulted in miscarriage at 8 weeks, it was tested and caused by a chromosomal issue). Next two cycles were failures. The only change was these embryos were all PGS tested. Each cycle was a “natural” FET cycle inserting day 5 blastocyst, only medication was progesterone suppositories. I’ve been tested for antibodies/NK cells and they are not elevated. Any ideas or suggestions on what is causing the issue here? Any advice or suggestions greatly appreciated.
To start with let me say that while I respect your statement that immune tests were normal, that might well be in the eyes of the beholder. It is very important that the tests be done in one of about 5 reproductive immunology reference labs in the country and that the correct tests be done. For example, when it comes to NK cell activity, the performance of a K-562 target cell test is crucial. Measuring the concentration of these cells is not helpful at all. Since this is such an important issue, I suggest you either contact m to discuss or you post the results on this board and I will review them. The former is by far preferable.
Geoffrey Sher MD
When it comes to reproduction, humans are the poorest performers of all mammals. In fact we are so inefficient that up to 75% of fertilized eggs do not produce live births, and up to 30% of pregnancies end up being lost within 10 weeks of conception (in the first trimester). RPL is defined as two (2) or more failed pregnancies. Less than 5% of women will experience two (2) consecutive miscarriages, and only 1% experience three or more.
Pregnancy loss can be classified by the stage of pregnancy when the loss occurs:
•Early pregnancy loss (first trimester)
•Late pregnancy loss (after the first trimester)
•Occult “hidden” and not clinically recognized, (chemical) pregnancy loss (occurs prior to ultrasound confirmation of pregnancy)
•Early pregnancy losses usually occur sporadically (are not repetitive).
In more than 70% of cases the loss is due to embryo aneuploidy (where there are more or less than the normal quota of 46 chromosomes). Conversely, repeated losses (RPL), with isolated exceptions where the cause is structural (e.g., unbalanced translocations), are seldom attributable to numerical chromosomal abnormalities (aneuploidy). In fact, the vast majority of cases of RPL are attributable to non-chromosomal causes such as anatomical uterine abnormalities or Immunologic Implantation Dysfunction (IID).
Since most sporadic early pregnancy losses are induced by chromosomal factors and thus are non-repetitive, having had a single miscarriage the likelihood of a second one occurring is no greater than average. However, once having had two losses the chance of a third one occurring is double (35-40%) and after having had three losses the chance of a fourth miscarriage increases to about 60%. The reason for this is that the more miscarriages a woman has, the greater is the likelihood of this being due to a non-chromosomal (repetitive) cause such as IID. It follows that if numerical chromosomal analysis (karyotyping) of embryonic/fetal products derived from a miscarriage tests karyotypically normal, then by a process of elimination, there would be a strong likelihood of a miscarriage repeating in subsequent pregnancies and one would not have to wait for the disaster to recur before taking action. This is precisely why we strongly advocate that all miscarriage specimens be karyotyped.
There is however one caveat to be taken into consideration. That is that the laboratory performing the karyotyping might unwittingly be testing the mother’s cells rather than that of the conceptus. That is why it is not possible to confidently exclude aneuploidy in cases where karyotyping of products suggests a “chromosomally normal” (euploid) female.
Late pregnancy losses (occurring after completion of the 1st trimester/12th week) occur far less frequently (1%) than early pregnancy losses. They are most commonly due to anatomical abnormalities of the uterus and/or cervix. Weakness of the neck of the cervix rendering it able to act as an effective valve that retains the pregnancy (i.e., cervical incompetence) is in fact one of the commonest causes of late pregnancy loss. So also are developmental (congenital) abnormalities of the uterus (e.g., a uterine septum) and uterine fibroid tumors. In some cases intrauterine growth retardation, premature separation of the placenta (placental abruption), premature rupture of the membranes and premature labor can also causes of late pregnancy loss.
Much progress has been made in understanding the mechanisms involved in RPL. There are two broad categories:
1.Problems involving the uterine environment in which a normal embryo is prohibited from properly implanting and developing. Possible causes include:
•Inadequate thickening of the uterine lining
•Irregularity in the contour of the uterine cavity (polyps, fibroid tumors in the uterine wall, intra-uterine scarring and adenomyosis)
•Hormonal imbalances (progesterone deficiency or luteal phase defects). This most commonly results in occult RPL.
•Deficient blood flow to the uterine lining (thin uterine lining).
•Immunologic implantation dysfunction (IID). A major cause of RPL. Plays a role in 75% of cases where chromosomally normal preimplantation embryos fail to implant.
•Interference of blood supply to the developing conceptus can occur due to a hereditary clotting disorder known as Thrombophilia.
2.Genetic and/or structural chromosomal abnormality of the embryo.Genetic abnormalities are rare causes of RPL. Structural chromosomal abnormalities are slightly more common but are also occur infrequently (1%). These are referred to as unbalanced translocation and they result from part of one chromosome detaching and then fusing with another chromosome. Additionally, a number of studies suggest the existence of paternal (sperm derived) effect on human embryo quality and pregnancy outcome that are not reflected as a chromosomal abnormality. Damaged sperm DNA can have a negative impact on fetal development and present clinically as occult or early clinical miscarriage. The Sperm Chromatin Structure Assay (SCSA) which measures the same endpoints are newer and possibly improved methods for evaluating.
IMMUNOLOGIC IMPLANTATION DYSFUNCTION
Autoimmune IID: Here an immunologic reaction is produced by the individual to his/her body’s own cellular components. The most common antibodies that form in such situations are APA and antithyroid antibodies (ATA).
But it is only when specialized immune cells in the uterine lining, known as cytotoxic lymphocytes (CTL) and natural killer (NK) cells, become activated and start to release an excessive/disproportionate amount of TH-1 cytokines that attack the root system of the embryo, that implantation potential is jeopardized. Diagnosis of such activation requires highly specialized blood test for cytokine activity that can only be performed by a handful of reproductive immunology reference laboratories in the United States.
Alloimmune IID, i.e., where antibodies are formed against antigens derived from another member of the same species, is believed to be a relatively common immunologic cause of recurrent pregnancy loss.
Autoimmune IID is often genetically transmitted. Thus it should not be surprising to learn that it is more likely to exist in women who have a family (or personal) history of primary autoimmune diseases such as lupus erythematosus (LE), scleroderma or autoimmune hypothyroidism (Hashimoto’s disease), autoimmune hyperthyroidism (Grave’s disease), rheumatoid arthritis, etc. Reactionary (secondary) autoimmunity can occur in conjunction with any medical condition associated with widespread tissue damage. One such gynecologic condition is endometriosis. Since autoimmune IID is usually associated with activated NK and T-cells from the outset, it usually results in such very early destruction of the embryo’s root system that the patient does not even recognize that she is pregnant. Accordingly the condition usually presents as “unexplained infertility” or “unexplained IVF failure” rather than as a miscarriage.
Alloimmune IID, on the other hand, usually starts off presenting as unexplained miscarriages (often manifesting as RPL). Over time as NK/T cell activation builds and eventually becomes permanently established the patient often goes from RPL to “infertility” due to failed implantation. RPL is more commonly the consequence of alloimmune rather than autoimmune implantation dysfunction.
However, regardless, of whether miscarriage is due to autoimmune or alloimmune implantation dysfunction the final blow to the pregnancy is the result of activated NK cells and CTL in the uterine lining that damage the developing embryo’s “root system” (trophoblast) so that it can no longer sustain the growing conceptus. This having been said, it is important to note that autoimmune IID is readily amenable to reversal through timely, appropriately administered, selective immunotherapy, and alloimmune IID is not. It is much more difficult to treat successfully, even with the use of immunotherapy. In fact, in some cases the only solution will be to revert to selective immunotherapy plus using donor sperm (provided there is no “match” between the donor’s DQa profile and that of the female recipient) or alternatively to resort to gestational surrogacy.
DIAGNOSING THE CAUSE OF RPL
In the past, women who miscarried were not evaluated thoroughly until they had lost several pregnancies in a row. This was because sporadic miscarriages are most commonly the result of embryo numerical chromosomal irregularities (aneuploidy) and thus not treatable. However, a consecutive series of miscarriages points to a repetitive cause that is non-chromosomal and is potentially remediable. Since RPL is most commonly due to a uterine pathology or immunologic causes that are potentially treatable, it follows that early chromosomal evaluation of products of conception could point to a potentially treatable situation. Thus I strongly recommend that such testing be done in most cases of miscarriage. Doing so will avoid a great deal of unnecessary heartache for many patients.
Establishing the correct diagnosis is the first step toward determining effective treatment for couples with RPL. It results from a problem within the pregnancy itself or within the uterine environment where the pregnancy implants and grows. Diagnostic tests useful in identifying individuals at greater risk for a problem within the pregnancy itself include:
•Karyotyping (chromosome analysis) both prospective parents
•Assessment of the karyotype of products of conception derived from previous miscarriage specimens
•Ultrasound examination of the uterine cavity after sterile water is injected or sonohysterogram, fluid ultrasound, etc.)
•Hysterosalpingogram (dye X-ray test)
•Hysteroscopic evaluation of the uterine cavity
•Full hormonal evaluation (estrogen, progesterone, adrenal steroid hormones, thyroid hormones, FSH/LH, etc.)
•Immunologic testing to include:
a)Antiphospholipid antibody (APA) panel
b)Antinuclear antibody (ANA) panel
c)Antithyroid antibody panel (i.e., antithyroglobulin and antimicrosomal antibodies)
d)Reproductive immunophenotype
e)Natural killer cell activity (NKa) assay (i.e., K562 target cell test)
f)Alloimmune testing of both the male and female partners
TREATMENT OF RPL
Treatment for Anatomic Abnormalities of the Uterus: This involves restoration through removal of local lesions such as fibroids, scar tissue, and endometrial polyps or timely insertion of a cervical cerclage (a stitch placed around the neck of the weakened cervix) or the excision of a uterine septum when indicated.
Treatment of Thin Uterine Lining: A thin uterine lining has been shown to correlate with compromised pregnancy outcome. Often this will be associated with reduced blood flow to the endometrium. Such decreased blood flow to the uterus can be improved through treatment with sildenafil and possibly aspirin.
Sildenafil (Viagra) Therapy. Viagra has been used successfully to increase uterine blood flow. However, to be effective it must be administered starting as soon as the period stops up until the day of ovulation and it must be administered vaginally (not orally). Viagra in the form of vaginal suppositories given in the dosage of 25 mg four times a day has been shown to increase uterine blood flow as well as thickness of the uterine lining. To date, we have seen significant improvement of the thickness of the uterine lining in about 70% of women treated. Successful pregnancy resulted in 42% of women who responded to the Viagra. It should be remembered that most of these women had previously experienced repeated IVF failures.
Use of Aspirin: This is an anti-prostaglandin that improves blood flow to the endometrium. It is administered at a dosage of 81 mg orally, daily from the beginning of the cycle until ovulation.
Treating Immunologic Implantation Dysfunction with Selective Immunotherapy: Modalities such as IL/IVIg, heparinoids (Lovenox/Clexane), and corticosteroids (dexamethasone, prednisone, prednisolone) can be used in select cases depending on autoimmune or alloimmune dysfunction.
The Use of IVF in the Treatment of RPL
In the following circumstances, IVF is the preferred option:
1.When in addition to a history of RPL, another standard indication for IVF (e.g., tubal factor, endometriosis, and male factor infertility) is superimposed.
2.In cases where selective immunotherapy is needed to treat an immunologic implantation dysfunction.
The reason for IVF being a preferred approach in such cases is that in order to be effective, the immunotherapy needs to be initiated well before spontaneous or induced ovulation. Given the fact that the anticipated birthrate per cycle of COS with or without IUI is at best about 15%, it follows that short of IVF, to have even a reasonable chance of a live birth, most women with immunologic causes of RPL would need to undergo immunotherapy repeatedly, over consecutive cycles. Conversely, with IVF, the chance of a successful outcome in a single cycle of treatment is several times greater and, because of the attenuated and concentrated time period required for treatment, IVF is far safer and thus represents a more practicable alternative
Since embryo aneuploidy is a common cause of miscarriage, the use of preimplantation genetic diagnosis (PGD), with tests such as CGH, can provide a valuable diagnostic and therapeutic advantage in cases of RPL. PGD requires IVF to provide access to embryos for testing.
There are a few cases of intractable alloimmune dysfunction due to absolute DQ alpha matching where Gestational Surrogacy or use of donor sperm could represent the only viable recourse, other than abandoning treatment altogether and/or resorting to adoption. Other non-immunologic factors such as an intractably thin uterine lining or severe uterine pathology might also warrant that last resort consideration be given to gestational surrogacy.
The good news is that if a couple with RPL is open to all of the diagnostic and treatment options referred to above, a live birthrate of 70%–80% is ultimately achievable.
I invite you to call 702-699-7437 or 800-780-7437 or go online on this site and set up a one hour Skype consultation with me to discuss your case in detail.
I also suggest that you access the 4th edition of my book ,”In Vitro Fertilization, the ART of Making Babies”. It is available as a down-load through http://www.Amazon.com or from most bookstores and public libraries.
Geoff Sher
the tests done and the
can you tell me more about Reproductive Immunology Associates (RIA), and how it’s tested?
Give them a call and they will explain to you! Go to Google for contact information.
I have worked with Dr William Matzner of RIA at both the clinical and research levels for >2 deecades. In my opinion RIA is the best reproductive immunology lab in the country.
Dear Dr. Sher,
Good morning. Request your expert advice on this topic.
I had done mini IVF last 2 times. Both times on day 7 a couple of follicles would be seen on day 7.
Protocol followed was this From day 7 onwards, every alternate day, Gonal 300 or Follitism was provided. From Day 8 , a tag Cetrotide would be started.
My concern is while the follicles show good growth until Day 7, after that only one dominant follicle starts growing bigger while the others stop growing. Eventually at egg collection time, only one egg ( from the dominant follicle) was retrieved.
Please advise what can be done to address the dominant follicle problem.
1. Is it because of the low dose of Gonal or Follitism, should it be higher ?
2. Are we starting the Antag ( Cetrotide) at the right time or should we do it only after Day 10 or so
3. are there any other reasons for the dominant follicle occurrence.
Kindly advise
Regards- Dhivya
Thank you
In my opinion, this relates to the protocol used in your case which probably is not suitable.
Please visit my new Blog on this very site, http://www.DrGeoffreySherIVF.com, find the “search bar” and type in the titles of any/all of the articles listed below, one by one. “Click” and you will immediately be taken to those you select. Please also take the time to post any questions or comments with the full expectation that I will (as always) respond promptly.
•Controlled Ovarian Stimulation (COS) for IVF: Selecting the ideal protocol
•Ovarian Stimulation for IVF using GnRH Antagonists: Comparing the Agonist/Antagonist Conversion Protocol.(A/ACP) With the“Conventional” Antagonist Aproach
•IVF: Factors Affecting Egg/Embryo “competency” during Controlled Ovarian Stimulation(COS)
•Anti Mullerian Hormone (AMH) Measurement to Assess Ovarian Reserve and Design the Optimal Protocol for Controlled Ovarian Stimulation (COS) in IVF.
•The “Biological Clock” and how it should Influence the Selection and Design of Ovarian Stimulation Protocols for IVF.
•Diagnosing and Treating Infertility due to Diminished Ovarian Reserve (DOR)
•The BCP: Does Launching a Cycle of Controlled Ovarian Stimulation (COS). Coming off the BCP Compromise Response?
•Staggered IVF: An Excellent Option When. Advancing Age and Diminished Ovarian Reserve (DOR) Reduces IVF Success Rate
•Embryo Banking/Stockpiling: Slows the “Biological Clock” and offers a Selective Alternative to IVF-Egg Donation.
•Preimplantation Genetic Sampling (PGS) Using: Next Generation Gene Sequencing (NGS): Method of Choice.
•IVF Failure and Implantation Dysfunction: The Role of Endometrial Thickness, Uterine Pathology and Immunologic Factors
•Unexplained IVF Failure
•Why did my IVF Fail
•Traveling for IVF from Out of State/Country–
•A personalized, stepwise approach to IVF
•The Role of Nutritional Supplements in Preparing for IVF
I invite you to call 702-699-7437 or 800-780-7437 or go online on this site and set up a one hour Skype consultation with me to discuss your case in detail.
I also suggest that you access the 4th edition of my book ,”In Vitro Fertilization, the ART of Making Babies”. It is available as a down-load through http://www.Amazon.com or from most bookstores and public libraries.
Geoff Sher
Hi Doctor Sher,
I just had my frozen embryo transfer yesterday 2/22, implanted 2 5day blastocyst, I had a fresh transfer last year that failed. I had an ERA test done that showed I’m receptive, I’m in estrogen 2mg twice aday, aspirin & IM 75 mg progesterone shot once a day, I also have a fibroid attached to the outside of my uterus wall which my doctor doesn’t feel will stop me from getting pregnant. I’m worried about the fibroid and was wondering what your position is about the fibroid effects on embryo transfers and my chances of getting pregnant having it not removed before my transfer. I hope to hear from you soon and thank you
Hi Rose,
The external fibroid is not the reason for your failure.
Whenever a patient fails to achieve a pregnancy following embryo transfer (ET), the first question asked is why! Was it simply due to, bad luck?, How likely is the failure to recur in future attempts and what can be done differently, to avoid it happening next time?.
It is an indisputable fact that any IVF procedure is at least as likely to fail as it is to succeed. Thus when it comes to outcome, luck is an undeniable factor. Notwithstanding, it is incumbent upon the treating physician to carefully consider and address the causes of IVF failure before proceeding to another attempt:
1.Age: The chance of a woman under 35Y of age having a baby per embryo transfer is about 35-40%. From there it declines progressively to under 5% by the time she reaches her mid-forties. This is largely due to declining chromosomal integrity of the eggs with advancing age…”a wear and tear effect” on eggs that are in the ovaries from birth.
2.Embryo Quality/”competency (capable of propagating a viable pregnancy)”. As stated, the woman’s age plays a big role in determining egg/embryo quality/”competency”. This having been said, aside from age the protocol used for controlled ovarian stimulation (COS) is the next most important factor. It is especially important when it comes to older women, and women with diminished ovarian reserve (DOR) where it becomes essential to be aggressive, and to customize and individualize the ovarian stimulation protocol.
We used to believe that the uterine environment is more beneficial to embryo development than is the incubator/petri dish and that accordingly, the earlier on in development that embryos are transferred to the uterus, the better. To achieve this goal, we used to select embryos for transfer based upon their day two or microscopic appearance (“grade”). But we have since learned that the further an embryo has advanced in its development, the more likely it is to be “competent” and that embryos failing to reach the expanded blastocyst stage within 5-6 days of being fertilized are almost invariably “incompetent” and are unworthy of being transferred. Moreover, the introduction into clinical practice about a decade ago, (by Levent Keskintepe PhD and myself) of Preimplantation Genetic Sampling (PGS), which assesses for the presence of all the embryos chromosomes (complete chromosomal karyotyping), provides another tool by which to select the most “competent” embryos for transfer. This methodology has selective benefit when it comes to older women, women with DOR, cases of unexplained repeated IVF failure and women who experience recurrent pregnancy loss (RPL).
3.The number of the embryos transferred: Most patients believe that the more embryos transferred the greater the chance of success. To some extent this might be true, but if the problem lies with the use of a suboptimal COS protocol, transferring more embryos at a time won’t improve the chance of success. Nor will the transfer of a greater number of embryos solve an underlying embryo implantation dysfunction (anatomical molecular or immunologic).Moreover, the transfer of multiple embryos, should they implant, can and all too often does result in triplets or greater (high order multiples) which increases the incidence of maternal pregnancy-induced complications and of premature delivery with its serious risks to the newborn. It is for this reason that I rarely recommend the transfer of more than 2 embryos at a time and am moving in the direction of advising single embryo transfers …especially when it comes to transferring embryos derived through the fertilization of eggs from young women.
4.Implantation Dysfunction (ID): Implantation dysfunction is a very common (often overlooked) cause of “unexplained” IVF failure. This is especially the case in young ovulating women who have normal ovarian reserve and have fertile partners. Failure to identify, typify, and address such issues is, in my opinion, an unfortunate and relatively common cause of repeated IVF failure in such women. Common sense dictates that if ultrasound guided embryo transfer is performed competently and yet repeated IVF attempts fail to propagate a viable pregnancy, implantation dysfunction must be seriously considered. Yet ID is probably the most overlooked factor. The most common causes of implantation dysfunction are:
a.A“thin uterine lining”
b.A uterus with surface lesions in the cavity (polyps, fibroids, scar tissue)
c.Immunologic implantation dysfunction (IID)
d.Endocrine/molecular endometrial receptivity issues
5.The cause of the infertility: Certain causes of infertility are repetitive and thus cannot readily be reversed. Examples include advanced age of the woman; severe male infertility; immunologic infertility associated with alloimmune implantation dysfunction (especially if it is a “complete DQ alpha genetic match between partners plus uterine natural killer cell activation (NKa)
Patients often ask me the question…”When should I stop doing IVF” or “when should I move on to egg donation and/or gestational surrogacy?”. The answer does not lie solely in the number of prior attempts made. Rather it is “when in spite of thorough evaluation” there is no “remediable/treatable cause” for failure that can be identified.
Please visit my new Blog on this very site, http://www.DrGeoffreySherIVF.com, find the “search bar” and type in the titles of any/all of the articles listed below, one by one. “Click” and you will immediately be taken to those you select. Please also take the time to post any questions or comments with the full expectation that I will (as always) respond promptly.
•Controlled Ovarian Stimulation (COS) for IVF: Selecting the ideal protocol
•Ovarian Stimulation for IVF using GnRH Antagonists: Comparing the Agonist/Antagonist Conversion Protocol.(A/ACP) With the“Conventional” Antagonist Aproach
•IVF: Factors Affecting Egg/Embryo “competency” during Controlled Ovarian Stimulation(COS)
•The BCP: Does Launching a Cycle of Controlled Ovarian Stimulation (COS). Coming off the BCP Compromise Response?
•Staggered IVF: An Excellent Option When. Advancing Age and Diminished Ovarian Reserve (DOR) Reduces IVF Success Rate
•Preimplantation Genetic Sampling (PGS) Using: Next Generation Gene Sequencing (NGS): Method of Choice.
•IVF Failure and Implantation Dysfunction: The Role of Endometrial Thickness, Uterine Pathology and Immunologic Factors
•Why did my IVF Fail
•Immunologic Implantation Dysfunction (IID) & Infertility (IID):PART 1-Background
•Immunologic Implantation Dysfunction (IID) & Infertility (IID):PART 2- Making a Diagnosis
•Immunologic Dysfunction (IID) & Infertility (IID):PART 3-Treatment
•Thyroid autoantibodies and Immunologic Implantation Dysfunction (IID)
•Traveling for IVF from Out of State/Country–
•A personalized, stepwise approach to IVF
I invite you to call 702-699-7437 or 800-780-7437 or go online on this site and set up a one hour Skype consultation with me to discuss your case in detail.
I also suggest that you access the 4th edition of my book ,”In Vitro Fertilization, the ART of Making Babies”. It is available as a down-load through http://www.Amazon.com or from most bookstores and public libraries.
Geoff Sher
Dr. Sher, What is your view of embryos tested with mosaicism? I understand that some doctor say its abnormal and others say I can have a normal successful baby. Is it worth to transfer? Do I have a good chance? Or, is it only a small chance of a successful normal baby? Thanks. Heleln.
Thanks Helen,
Here from an article I wrote on this blog, is my response:
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 all aneuploid embryos we and in so doing, 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.” 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 “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 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 such a transfer, 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 “autocorrect”, is a rational consideration. Needless to say, such action would require full disclosure, the completion 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).”.
I hope this helps.
Geoff Sher