2 Embryo Transfer Success Rate: Why a 2 Embryo Transfer is Best!

Published: 12/14/2015

If you look at ACFS data, you can not help but notice that the success with transferring two embryos is so much better than with transferring one. A short while ago, our embryologist asked "if a patient had 4 chromosomally normal embryos, would she have the same number of successful pregnancies (babies) if she transferred one at a time as opposed to doing two embryo transfers of two each?"

Logically, you would think that the outcome would be the same, unless there was the possibility that by transferring two embryos, one would "help" the other to implant by possibly secreting and/or releasing substances or "signals" that would promote implantation.

There has been a big push in the country to transfer only one embryo, mainly to avoid the risks of twins. So, if a patient has four embryos, the recommendation would be to transfer one at a time, until all four embryos would be transferred; as opposed to doing two transfers of two each.

ACFS respectfully disagrees with this advice.

2 Embryo Transfer Success Rates

As you can see from our data, a two embryo transfer is the way to go to achieve the "best" success rates.

This is especially true for women 37 or older. ACFS current data represents the fact that most one embryo transfers are either in younger patients who want a "zero" risk of twins or older patients (37 or older) who only have one chromosome normal embryo to transfer. This suggests, that although chromosome testing (PGS) "goes a long way in eliminating age as a factor", it does not completely wipe it out.

Two Embryo Transfer Chance of Twins / Twin Rates

This is evidenced by ACFS data, that shows that the twinning rate at 37 years old or greater is 8% with a two embryo transfer; whereas, less than 37 years old it is 28% with the same number of embryos.

Therefore, in order to achieve the "highest success rate possible", ACFS strongly recommends a two embryo transfer. Of course, ACFS will always respect and support a patients choice in how many embryos she wants to transfer.

Why Fertility Clinics Push for Single Embryo Transfer (SET)?

ACFS has to wonder why clinics "push" a single embryo transfer (SET)?

Clearly, one reason is to avoid the risk of twins. Another is maybe the end result of transferring one embryo at a time, eventually results in the same number of successful pregnancies. The third..., should not even be considered as a possibility!

But something very important is missing in all this - that although the end result of a single embryo transfer may be the same (ACFS is not 100% sure of this) in the amount of overall successful pregnancies it produces, this thinking fails to consider several very important points:

  1. The emotional impact of the disappointment with the news of a failed transfer.
  2. The financial burden of having to possibly do multiple embryo transfers (ET) as opposed to doing one.
  3. The physical-ness (shots, appointments and time loss) in preparing for each embryo transfer.
  4. Some patients do not actually view twins as a bad outcome, and many prefer it (http://www.fertstert.org/article/S0015-0282(08)00520-7/abstract).

There is no question in ACFS mind that an elective single embryo transfer (eSET) in everyone would produce higher pregnancy rates than our current data of 57.7% which is clearly biased (see above comments); however, there is also no question it would not be close to the success of 84.6% with a two embryo transfer; and thus, statistically would require more transfers.

ACFS's goal is not to see how fast we can help you get pregnant (short protocols / fresh transfers), or how many embryos transfers we can do; but to get each and every patient pregnant on their first attempt. A second attempt is for a second pregnancy

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