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Blastocyst Transfer
For a general discussion on this subject, go to to Page 1 of Blastocyst
Transfer
2 blastocysts that were transferred with a pregnancy resulting
Transferring 2 blastocysts can yield high pregnancy rates and (almost) no
risk for triplets
Blastocyst Images from our IVF Lab
Unresolved issues regarding blastocyst transfer:
1. Will blastocyst transfer improve pregnancy rates for a few couples, for
many couples, or for almost all couples undergoing IVF?
2. Which patients are the ones that will benefit the most? How do we select
the most appropriate candidates?
3. How many blastocysts should we transfer?
Would 3 give too high a triplet rate?
Would 2 give too low a pregnancy rate?
Would it be reasonable to choose to transfer only one good blastocyst in some
cases?
4. How many couples will have no blastocysts for transfer if we culture to
day 5?
How will this figure vary according to the selection criteria used by the
IVF program for choosing patients for blastocyst transfer?
These questions should be resolved over the next several years.
Ten years ago, GIFT (egg and sperm transfer to the tubes) and ZIFT (one-day-
old embryo transfer to the tubes) were popular because IVF laboratories were
not able to attain high pregnancy rates with longer periods of in vitro
culture. Today, most programs have abandoned these much more expensive and
invasive tubal procedures and are routinely doing day 3 uterine transfers
with much improved pregnancy rates. Now that we have learned more about human
embryonic needs and are improving our IVF culture systems, we are moving
toward more routine use of blastocyst transfer. This will allow our patients
the highest possible pregnancy rates while reducing their risk for multiple
pregnancy.
Our IVF program and some others are currently doing blastocyst transfers in
selected cases. Very few programs are doing all of their IVF cases with day
5 transfers. In almost all centers (including ours) that do blastocyst
Transfer, there are selection criteria for deciding which cases can be done
as blastocyst transfer vs. day 3 transfer. Usually, the criteria are related
to one or more of the following factors:
1. The number of follicles on the day of HCG
2. The number of fertilized eggs
3. The number of good quality embryos on day 3
This means that only "good" cases are allowed to have blastocyst transfer at
most centers. Because of this "selection bias" for the better cases,
pregnancy rates would be expected to be higher with blastocyst transfers as
compared to day 3 transfers. We need to be careful about how we interpret
this. For example, a program might have a 30% pregnancy rate for day 3
transfers and a 65% pregnancy rate for day 5 transfers. Patients (and the
media in the US) might then think that couples undergoing IVF should have
blastocyst transfer so they will have a much better chance for pregnancy.
However, in reality, if the program did all of their cases as day 5 transfers,
the pregnancy rate would be somewhere in between the previous day 3 and day
5 rates - and most likely the overall pregnancy rate for the program would be
no better or no worse than before.
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