Q from U: How many embryos should I transfer?

September 26, 2014Carole 6 Comments »

The question of how many embryos to transfer in a fresh IVF transfer comes up fairly often in one form or another. The question below is derived from one recently asked.
Q:. I’m starting my first IVF cycle, just before I turn 41. At age 37/38, I had done two cycles to freeze eggs, and so have about 30 eggs on ice. I am scheduled to do a fresh cycle because that a fresh cycle is covered by my insurance and a frozen embryo transfer cycle is not. The clinic is pushing me to agree to a single embryo transfer, even before I know if I get any eggs, let alone embryos.  I know that in most cases, a singleton pregnancy is safer than a multiple pregnancy but on the other hand I know my age makes it very unlikely any given embryo will implant. Do you have any information that would be helpful to be in making this decision?

A: Yes!!, there is a resource to help doctors (and patients) make these decisions. The American Society for Reproductive Medicine (ASRM) publishes guidelines for how many embryos to transfer. This document is free for download to anyone from this link:  I have recreated the table from the article below.

Stage-Prognosis Under 35 35-37 38-40 41-42
Cleavage -Favorable 1-2 2 3 5
Cleavage-Other 2 3 4 5
Blastocysts- Favorable 1 2 2 3
Blastocysts – Other 2 2 3 3

These professional guidelines are written by a committee of physicians and represent a consensus view of what is a reasonable number of embryos to transfer for most patients depending on three factors- maternal age, stage of the embryo (day 3 cleavage or day 5 blastocyst) and whether the prognosis for pregnancy is favorable or “other”.

The patient’s maternal age is the largest contributing factor to infertility, followed by every other infertility factor. If a patient has no or few other factors that could decrease their chances of getting pregnant, they have a ‘favorable” expectation of pregnancy from the transfer. Alternatively, if they have other variables that make it less likely that they will achieve pregnancy, then they have an unfavorable prognosis or as termed in the guidelines– “other” than favorable prognosis.

The transfer number recommendation is an attempt to balance the need to increase the patient’s chance of getting pregnant at all (transfer more embryos) while decreasing the chance of a multiple pregnancy occurring  which could end badly for the patient (transfer fewer embryos).

As we age, our chance of pregnancy plummets because more of our eggs, (and therefore our embryos), will have an abnormal number of chromosomes which makes the embryo unable to progress in pregnancy even if it initially implants. To compensate for this, it is suggested that more embryos be transferred per attempt in older patients.

The older patient who asked the question about how many to transfer was being encouraged to transfer only a single embryo – which falls outside of these recommendations. It is possible that her doctor has made a judgement that ANY chance of multiples is too hazardous for this particular patient- perhaps because of some  known uterine issues specific to this patient.

More and more embryo transfers are made with blastocyst stage embryos. Why transfer fewer blastocyst embryos than cleavage stage embryos? The reason is that embryos that reach blastocyst stage have proven that they are healthier than another embryo that stalls out on day 3 or 4 and never makes it to blastocyst stage. If you are transferring on day 3, you have less information about the embryos and so have to assume some will stall out, so more are typically transferred on day 3. Of course, if your embryos are all good on day 3, you have just really increased your chances of a multiple pregnancy- !- which is a problem and  is why day 3 transfers are falling out of fashion.

Patients should understand that they have a right to ask the doctor to explain why they are recommending one course of clinical action over another. Most doctors don’t mind doing this at all. If you encounter a lot of resistance to questions or the answers don’t make a lot of sense, it might be time to find another doctor who is more accepting of their role as educator and health care partner.

Any professional recommendation may change for a particular patient based on additional or new  information that may be available. For instance,  pre-implantation genetic testing (PGD)  to identify embryos that are genetically abnormal from those that are normal can result in a recommendation that only one embryo be transferred. If only normal embryos are transferred, it is  more likely that the normal embryo will implant –and stay!!- than an abnormal one.  The table above assumes that we have no genetic information- and some of the embryos available will be normal and more likely to result in a good pregnancy and others will be abnormal and have little or  no chance of creating a viable pregnancy. So if a doctor has a known group of normal embryos to choose from, typically, they are inclined transfer fewer or just one in a single transfer attempt.

When cryopreservation of embryos was less successful than it is today, the thawed embryos would be partially damaged and not look so good at thaw. Because they were considered lower quality in terms of their odds of implanting, more thawed embryos would be transferred to a patient in a thaw cycle than a fresh cycle. Today, vitrified embryos look as good as fresh, so there is no need to transfer more previously-vitrified embryos.

In a case where the embryos are derived from donor eggs, the recommendation to transfer disregards the age of the recipient (intended mother) all together. Most donors are well below 35 years of age, so the recommended number to transfer will be based on this age group, not the age of the intended mother.

Medicine is still more an art than a science, and although we are always on the lookout for more tests to give us more information to make better decisions and recommendations, there is still lots of gray area where the physician leans on his/her experience in addition to the data.  I think it is useful for patients to understand the professional guidelines that exist, especially when their doctor recommends a course of action outside of the professional guidelines. Hopefully, this will lead to better conversations between doctors and patients.

© 2014, Carole. All rights reserved.

6 Responses to this entry

  • Katie Says:

    Hi Carole,
    Thanks again for the answer on this. I think I left out the other part of the equation–the CCS testing, which you mention above. I am being asked-as I start the cycle–not only about the # of embryos I’d want implanted, but whether I want to do CCS (cost of 4500 dollars).

    I definitely want to do CCS if I have 3 or more embryos that make it to that blastocyte stage. If I have any normal ones from the CCS, I would agree to an eSET. I’ve seen the trial results from the doctors at RMANJ who have shown almost equivalent pregnancy rates of CCS+eSET as nontested DET.

    My agonizing right now is about whether to say I want to do CCS if I only get 1 or 2 embryos. It seems like a lot of money to do it for just 1 or 2 embryos. Would I be better off taking a shot and having the 1 or 2 implanted and see how it goes?

    I think the answer may lie in my age, in that there is such a high rate of abnormalities. Is it better to spend the money and avoid the (high?) chance of miscarriage so that I can move quickly to another cycle if needed, versus “wasting time” with trying for a transfer and potentially short-lived pregnancy? To me, the twin risk in this scenario is pretty low for exactly that chromosomal/age reason, though I don’t have statistics on that.

    Do you have any thoughts or stats that would help me think this through? Am I just having a cognitive bias driven by the dollar signs??

  • Carole Says:

    Hi Katie,
    So several things. 1. How important is it to you minimize the chances of miscarriage or no implantation or having a Downs affected child? If avoiding any of those things is very important to you, then the testing should give you information to transfer only normal embryos and lessen the chance of any of these outcomes.
    2. Older women tend to have fewer embryos. Among the embryos they do have, it is more likely that some will be abnormal, so it is possible that you may have no embryos to transfer- after testing. No transfer is a risk of testing so you have to factor that in.
    3. What some patients choose to do to maximize the number of embryos available for testing and to minimize the cost of CCS is to do several fresh fresh IVF cycles in a row and stockpile embryos for one thaw, biopsy and CCS testing procedure. Not all clinics offer this option but it might be something to consider- especially if you have IVF insurance for fresh cycles.
    There isn’t a right or wrong answer here; it depends on your appetite for risk and your budget. I would talk to your partner and havea follow-up conversation with your doctor to see what options you have. Good Luck!! Carole

  • Denise Says:

    Hi Carole. I ended up gaving a miscarriage after my two blastocyst transfer. I am scheuled for another transfer on Dec 4th but I only have one good embryo left. 🙁 it is an AA embryo. Are my odds of pregnancy very low with only one? They are hoping to get a second one for me before the 4th.

  • Carole Says:

    Hi Denise,
    There are a lot of variables but if the one embryo is healthy and your uterine lining is receptive, one is all you need. I am so sorry for your loss and wish you MUCH GOOD LUCK going forward!! Carole

  • Lynette Says:

    Hi Carole,
    Hope you can help me answer this question. I’m 36 year old this year, conceived naturally 2 years ago & miscarried at 14 weeks due to fetal Down Syndrome & hydrops fetalis. After 18 months of trying,we have decided on IUI x 1 cycle (failed) and IVF x 1 cycle at an academic medical centre. Pre-conception tests on both hubby and I were normal. On my fresh D5 ET, I’ve gotten pregnant. However, I lost this pregnancy at 8 weeks. From the hyperstimulation protocol, I had 11 matured oocytes. However, in the end, besides the fresh embryo, I now have 3 vitrified D6 embryos of good quality in storage. However, my country does not allow CCS/PGD/PGS. 1. Can you do CCS/PGS on frozen embryos after you thaw them?
    2. Would you recommend a totally fresh hyperstimulation cycle if I am worried about oocyte quality in the previous cycle?

  • Carole Says:

    Hi Lynette, Yes you can do PGS on thawed embryos- the main issue is how long does it take to get results back? If you can get same day results on a day 6 embryo, it might not be too late to transfer on day 6. If you need a few days to get results back, a day 6 embryo will likely be too old by the time it is transferred (embryos don’t do well in culture past day 6) . A day 3 embryo could be thawed, biopsied and then left in culture or even refrozen because you have time remaining to get results back. Regarding another egg stim cycle, because of your older age and past history, I think IVF has not been very kind to you and is unlikely to yield better results in future cycles. It may be time to consider other paths to parenthood. Good Luck!! Carole

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