What is Blastocyst Culture?
cycles, the embryos are transferred back into the womb, on
the second or third day after egg collection. This standardized
method of day 2 or day 3 transfer yields good pregnancy rates.
However this method has some disadvantages:
1.In the natural cycle
the embryo is conceived in the fallopian tube. After this
it takes 4 days for it to travel to the womb. By this time
the embryo develops into mature stage called the Blastocyst,
which then implants into the lining of the womb. In standard
IVF or ICSI, we put back the embryos 2-3 days before they
reach the Blastocyst stage. By putting the embryos back at
the Blastocyst stage, there is an increase in pregnancy rates.
2.When we put back the
embryos on day 2 or day 3, we
are not very sure as to which embryo is viable or will survive
and grow to the Blastocyst stage and be implanted. Hence we
tend to place 2 to 4 embryos into the womb, to try and increase
the pregnancy rates. This results in an increase in pregnancy
rates, but also gives rise to increase incidence of multiple
pregnancies. Multiple pregnancies have their own set of problems
such as miscarriage and pre-term births.
Keeping in view, the above, many units, including ours, are
now growing embryos in the Incubator, for 5 days, till they
reach the mature Blastocyst stage, and then placing them back
into the womb. This is known as Blastocyst transfer.
How is Blastocyst Culture done?
Major steps in the sequence are:
Monitor the development of ripening egg(s) in the ovaries.
Put eggs and sperm
together in the laboratory, and provide correct conditions
for fertilization and early embryo growth. (Through the IVF
or ICSI procedure)
The embryos obtained
on Day 2 (2-4 cell stage) are placed in special sequential
culture media and grown to Blastocyst stage. This takes 5
to 6 days after egg retrieval.
Normally 50 -60% of
embryos develop into Blastocyst.
Two good quality Blastocyst
are then selected, loaded into the transfer catheter and standard
embryo transfer is done.
The remaining Blastocyst
can be frozen for later use, in subsequent cycles.
to embryo transfer, the cover of the Blastocyst may be cut
with a Laser or may be dissolved with an enzyme called Pronase
. Research has shown this to increase pregnancy rates.
Why is Blastocyst culture not done
routinely for all patients?
In 20 -30 % of patients, none of the embryos develop into
Blastocyst. In these patients, there would be no viable embryo,
available for embryo transfer. In such a patient the pregnancy
chance will be zero.
This is a relatively new technique, and one does not know
whether there would be long term adverse effects in exposing
embryos for 5 days to the environment. At the same time, it
would be important
to note that there has been
no increase in abnormalities in Blastocyst babies as compared
to day 2/3 transfer babies.
Who would qualify for Blastocyst Culture?
have failed to get pregnant after IVF/ICSI cycles
who have more than 3 Grade 1 /Grade 2 good 6-8 cell embryos
on day 3 after egg retrieval. In these cases, Blastocyst culture
will help in selecting better, genetically more normal embryos
and also help in reducing multiple births. This is the main
criteria for perfoming Blastocyst, at the Babies And Us Fertility
who want to undergo Pre-implantation
It is important to counsel the patient about the occasional
risk of zero Blastocyst formation and hence zero pregnancy.