The bank of embryo and the process of embryo Cryopreservation.
The bank of embryo and
the process of embryo
Who May Benefit from Egg Freezing?
the Success Rates and the factor that effect
What is Embryo Cryopreservation?
What are the Success Rates for Embryo Cryopreservation?
Are There Any Risks Associated With Embryo Cryopreservation?
Who May Benefit from Egg Freezing?
Young women newly diagnosed with cancer, wishing to
avoid damage to their eggs
Young women under age 38 years old wishing to delay
fertility into the future.
Since 1984, thousands of babies have been born worldwide
after having undergone embryo cryopreservation.
This helps decrease the risk of multiple pregnancies
and gives couples the chance to space their children.
What is Embryo Cryopreservation?
When both animal and vegetable cells are simply frozen, their cell structure is destroyed
by the formation of ice crystals. To freeze embryos (and sperm) we add a protective
chemical known as a “cryoprotectant” to them which draws the water out of them so that
ice crystals do not form in them when they are frozen.
It is still not unusual for an embryo to lose one or more of its cells during the freeze/thaw
process. This does not significantly reduce the potential of the embryo to produce a
pregnancy unless more than half of its cells are lost. The loss of some cells also does not
cause any increased risk of fetal abnormalities.
Embryo cryopreservation, or embryo freezing, is one of the most common and well
established fertility preservation treatments, with proven successful pregnancy rates.
fertilizing them with sperm in a lab to create embryos that are then frozen for later use.
Embryos can be frozen at various stage – from one to five days after fertilization
(includes blastocyst stage) – as long as they are of good quality.
Cleavage stage embryos (2-16 cells on days 2-3) and blastocyst stage embryos (days
The embryo freezing process takes approximately 3 hours. Embryos are
sequentially treated with varying concentrations of a special solution,
called the cryoprotectant. The cryoprotectant protects the embryos
during the freezing process. Each embryo is then drawn into a specially
designed sterile straw that is uniquely labelled for the patient. The
straws containing the embryos are placed into a freezing machine,
slowly cooled to -35oC and stored in liquid nitrogen for longterm
storage ( -196 centigrad )
Essential requirements before freezing embryos
Written consents from both partners/donors.
•Both partners/donors are screened for infectious
diseases – HIV, Hepatitis B. Hepatitis C and Syphilis.
Embryo Cryopreservation from first to end…..
Transfer of cryopreserved/thawed embryos consists of:
1. Preparation of endometrial lining
2. Thawing and culture of cryopreserved embryos
3.Establishment of pregnancy
The treatment required to freeze embryos takes approximately 2 weeks. ( also depend on cancer
treatment , the entire process can take anywhere from 2 to 6 weeks to complete. ) (Lupron
injections begin. Lupron "puts ovaries to sleep" and temporarily stops their production of estrogen
and progesterone. The endogenous estrogen and progesterone secretion would interfere with the
development of the endometrial lining. Lupron injections are given for approximately four weeks.)
Hormones (birth control pills and / or Lupron®) will be used to suppress
ovulation and provide for better control of your hormones and ultimately the
timing of the embryo transfer.
But for before transfer :
(The first part of the process takes approximately 10-12 days, and requires daily,
self-administered hormone injections to stimulate egg development, as well as
blood tests and ultrasounds to monitor your hormone levels and the
development of your eggs. Side effects may include, discomfort and mood
One clear fact has emerged from this experience – poor quality
embryos do not survive the freeze-thaw process. Embryos which have
even sized cells within them and little fragmentation have a good
chance of surviving being frozen. Embryos whose cells are uneven in
size and which contain large numbers of fragments have a poor chance
of surviving freezing.
A good quality embryo with even sized cells and This embryo would be highly
likely to survive being frozen and thawed. (1)
A poor quality embryo with uneven sized cells .This embryo would not be
frozen due to its poor chances of surviving the freeze/thaw process. (2)
Thawing of Cryopreserved Embryos
Embryo thawing is the reverse of the freezing process, and involves
warming the embryos.
(Scientists will usually thaw the embryos the day before the scheduledembryo
transfer or On the day of your transfer, your embryos will be thawed. )
- Embryo thawing takes approximately 2 hours.
- embryos are returned to room temperature, the embryos are passed through a series
of solutions to remove the cryoprotectant that is no longer needed. The thawed
embryos are kept in the incubator until the embryo transfer, during which time they
should resume development and undergo cell division.
At the time of embryo cryopreservation, one to three embryos are stored
in a straw. You will need to decide how many of your straws should be
Unfortunately sometimes no embryos develop to the appropriate stage and are
therefore not suitable for transfer. The cycle will be cancelled at this time.
Frozen Embryo Transfer (FET)
The timing of the embryo transfer depends on a number of factors
including the cell stage of the embryo when frozen and uterine receptivity.
What are the Success Rates for
Success rates per embryo transfer from frozen embryos are approximately
30percent in the United States it is for past.
freezing and thawing, around 5% of patients will have the unfortunate
experience of none of their embryos surviving and therefore having their
frozen embryo transfer cancelled.
Due to the freezing and thawing process, the chances of having a baby using a
thawed frozen embryo are lower than with a fresh embryo.
Your chances of becoming pregnant with a thawed frozen embryo are not
affected by the length of time the embryo has been stored for.
Successful embryo cryopreservation depends on
Your age at the time of egg retrieval
Number and quality of eggs retrieved
Number of embryos frozen
Quality of the embryos frozen
Successful survival of the frozen embryos after thawing
Are There Any Risks Associated With Embryo
Hormone injections could theoretically stimulate the growth of hormone dependent
cancers such as breast and uterine cancers.
All women who take follicle-stimulating hormones are at risk for Ovarian
Hyperstimulation Syndrome (OHSS), a condition in which the ovaries become cystic
Side effects may also include nausea, headaches and allergic reaction at the injection
The time required for this option (at least 2 weeks) may delay the start of your cancer
treatment, which may not be ideal depending on the severity of your cancer. If you are
considering embryo cryopreservation, you should speak with your oncologist about the
potential impact on your cancer and/or the start of your cancer treatment.
There is no guarantee that a pregnancy will result even if embryo freezing is successful
and embryos are placed in your uterus.
Cryopreserved/thawed embryo transfer is identical to a ”fresh” embryo transfer.
There is no increased risk of birth defects in pregnancies from cryopreserved
embryos compared with conceptions conceived through intercourse.
Studies have found no conclusive evidence that the cryo and thawing of
embryos increases the probability of abnormalities in the resulting children.
Embryo freezing is a very delicate process. The fact that the embryos are also
delicate and fragile means the embryos that are frozen may not survive the
process of freezing and thawing, when it comes to using the frozen embryos for
transfer. Approximately about 70% of the frozen embryos survive the process of
freezing and thawing.