Q: What are blastocysts?
A - Blastocysts
are embryos that are five to six days of age (following
egg retrieval) and that have approximately 60 cells.
This is the stage at which embryos hatch and implant in the uterine wall. In healthy blastocysts, an inner cell mass (that will develop into
the fetus) can be identified as well as a blastocoele cavity
surrounded by cells that are destined to form the placenta.
Q - Why culture embryos to the
A - The longer period of time that elapses between egg retrieval and embryo transfer, the easier
is to see differences between good and poor quality embryos. By day five after egg retrieval,
embryos that have reached the blastocyst stage have distinguished themselves as the best quality
Embryos that are not blastocysts by day five or six are poor quality and are destined to
arrest in their
development. There may also be an advantage to transferring
embryos into the
uterus on day five because in "natural" conceptions, embryos don't arrive hi the uterine cavity
days following ovulation. Culturing embryos to the blastocyst stage thus allows us to
transfer fewer embryos (usually two) and maintain high rates
of success with much lower rates
Q - Is there any downside to blastocyst culture/transfer?
A - Yes. Some
patients' embryos may not grow to the blastocyst stage and thus they may not have any embryos to transfer on day five or six. While many believe
this is evidence for why a particular patient is unable to conceive,
this kind of outcome is very
troublesome and unsatisfying for patients and for then*
physicians. Fortunately, by choosing those patients
who are the best candidates for this procedure, this
outcome is very uncommon.
Q - Who is a candidate for blastocyst culture/transfer?
A - In our program,
we are offering blastocyst culture/transfer to patients at highest risk for a multiple pregnancy including those being treated with IVF/egg
donation and young patients (under age 35) who are doing
IVF with their own eggs. Blastocyst culture/transfer
may also be considered for patients of any age who have a large number of embryos. In all cases, we do not culture embryos beyond
day three unless there are at least two good quality 8-cell embryos on that day.
Q - Does ^ blastocyst transfer increase pregnancy rates?
A - Not necessarily.
Our primary goal with blastocyst transfer is to maintain high rates of success while decreasing the rate of multiple gestation. While h is true that
pregnancy rates may be higher for patients who transfer blastocysts, these results may
be biased because patients who are able to transfer
blastocysts usually have better quality embryos compared with those who are unable to do so.