EMBRYO TRANSFER

Transferring a fertilized embryo to a woman’s uterus is an important part of the in the vitro fertilization process.

    Embryo Transfer

    Transferring a fertilized embryo to a woman’s uterus is an important part of the in vitro fertilization process. An embryo transfer is the last part of the in vitro fertilization (IVF) process. During IVF, fertility medications are used to stimulate the ovaries into releasing healthy eggs. These eggs are then removed from a woman’s ovaries and fertilized in a lab. Once the fertilized eggs have multiplied, the embryos are transferred to the woman’s uterus. For a pregnancy to begin, the embryo must then attach itself to the wall of her womb or uterus.
    |IVF and embryo transfer is needed in cases where natural fertilization is not an option or has difficulty occurring. There are many reasons for embryo transfer, including:

    1. Ovulation disorders

    2. Damage to Fallopian tubes

    3. Endometriosis

    4. Genetic disorders

    The embryo transfer process is similar to the process for a pap smear. The doctor will insert a speculum into the woman’s vagina to keep the vaginal walls open. Using ultrasound for accuracy, the doctor will then pass a catheter through the cervix and into the womb. From there, the embryos are passed through the tube and into the womb. The process is usually pain-free and rarely requires any sedatives. Some women may feel discomfort as a result of having the speculum inserted or from having a full bladder, which is required for an ultrasound. The process is short, and the bladder can be emptied immediately after.
    Once fertilization has occurred, there are a few different options available for embryo transfer:
    Fresh embryo transfer: Once eggs have been fertilized, they are cultured for 3-5 days. The best embryos are chosen to transfer directly to the woman’s uterus.
    Frozen embryo transfer: Any healthy embryos that were not used in the first transfer can be frozen and stored for future use. These can be thawed and transferred to the uterus.
    Blastocyst embryo transfer: If many healthy embryos develop after fertilization, it is common to wait to see if the embryos develop into blastocysts.

    Fast Facts About Embryo Transfers:

    • An embryo transfer is a final stage in the In Vitro Fertilization (IVF) process where the fertilized egg—now an embryo—is placed in the woman’s uterus.
    • The embryo is loaded into a catheter, which is passed through the vagina and cervix and into the uterus where it is deposited.
    • This generally takes place between 3 and 5 days after egg retrieval if having a fresh transfer and anywhere from 4 weeks to years later if doing a frozen transfer.
    • There are many different types of embryo transfers: fresh, frozen, cleavage (day 3), a blastocyst (day 5), single, and multiple embryo transfers.
    • Today’s standard practice is to transfer one embryo (occasionally two) embryo(s) at a time.  This minimizes the chance of multiples while maintaining the same cumulative live birth rates (per retrieval) form an IVF cycle. Any remaining embryos from the IVF cycle are either frozen (if the first transfer is with fresh embryo) or remain frozen (if the first transfer if a frozen transfer – also called a freeze all cycle).

    What is an Embryo Transfer?

    An embryo transfer is the last stage in the IVF process, where the fertilized egg that has been left to grow for several days is placed in the woman’s uterus where it will hopefully implant, become a fetus, and result in the birth of a healthy child.

    The embryo transfer procedure is done by loading the IVF embryo into a catheter, which is then passed through the woman’s vagina and cervix, and deposited in the uterus.  Anesthesia is usually not necessary, but valium may be used.

    Types of Embryo Transfer:

    Just as the term implies, a fresh embryo transfer is the transfer of (an) embryo(s) that has not been frozen.

    Fresh Embryo Transfer

    A Frozen Embryo Transfer is a cycle in which frozen embryos from a previous IVF or donor egg cycle are thawed and then transferred into a woman’s uterus.

    A frozen embryo transfer may be done for a number of reasons:

    Medically Advised Due to Uterine Receptivity: During an IVF cycle, a woman is in a state of controlled ovarian hyperstimulation, which adds a good deal of physiological stress to the woman’s body.  In some cases, the woman’s body is unable to simultaneously prepare a beautiful “home” for the embryos to be transferred. If the woman has ovarian hyperstimulation syndrome or has elevated progesterone or estrogen levels or has a lining under 7mm at the time of trigger, it may be advised to do a “freeze all cycle,” followed by a FET.  This allows the intended mother to wait until the uterus/endometrium is more receptive and implantation more likely.

    A Second Embryo Transfer: In a conventional IVF cycle, it is common for 10-15 eggs to be produced through controlled hyperstimulation and result in a number of high-quality embryos available for transfer. Today’s standard practice is to transfer one (sometimes two) embryo into the woman’s uterus and freeze all remaining embryos to increase the chance of future pregnancy (should the couple want to continue expanding their family after giving birth or if the first transfer fails).

    Easier to plan: Because there are times when it is medically advised to convert a fresh cycle to a freeze all cycle with an FET, many, particularly travel clients, find it much easier to plan in advance for a frozen transfer as they are rarely ever canceled, can be easily planned, and offer comparable success rates as a fresh transfer.

    Cleavage (Day 3) Stage Embryo Transfer:

    Cleavage stage embryos are called such because the cells in the embryo are dividing (or cleaving), but the embryo itself is not growing in size. This stage is usually reached around day three but may happen on day two or four.  They have often referred to simply as “day three embryos.”

    Some fertility experts believe there’s no substitute for a woman’s uterus and that embryos should be put back into the uterine environment as quickly as possible. Since not all embryos survive until Day 5, transferring on Day 3 is a way to ensure an embryo gets to the optimal environment to thrive.  At Dr.INVITRO, we generally recommend transferring a day 5 embryo to select best quality embryo.

    Blastocyst (Day 5) Stage Embryo Transfer

    A blastocyst is an embryo that has developed into a single-layered sphere of cells encircling a fluid-filled cavity with a dense mass of cells grouped together.  Blastocysts contain anywhere from 60 to 120 cells.  This usually occurs on day five, but may happen on day 6, 7, or even 8. By this stage, the embryo has differentiated into two cell types:  the trophectoderm, the cells on the periphery of the embryo that forms the placenta, and the inner cell mass (ICM), the dense mass of cells on the inside that forms the fetus if the embryo implants.

    A blastocyst embryo is considered to be more “special” than an earlier stage embryo since it has a higher probability of being genetically normal, implanting, and leading to a live birth than a cleavage-stage embryo.

    By delaying embryo transfer to the blastocyst stage, an embryologist is better able to select embryos with a higher probability for continued development.

    An embryo that is grown to a blastocyst stage can also be genetically tested prior to transfer which can help reduce the risk of miscarriage for some populations, avoid known genetic disorders, and select the sex of the child.

    Single Embryo Transfer (SET or eSET)

    A(n) (Elective) Single Embryo Transfer is the practice of transferring only one embryo into a woman’s uterus. This offers a reduced chance of multiples while maintaining a very similar rate of pregnancy. Due to the reduced risk of an eSET along with having a very similar rate of pregnancy, eSET has quickly become the gold standard practice for transferring embryos with an IVF procedure.

    Multiple Embryo Transfer

    A transfer of multiple embryos is quite simply the transfer of more than one embryo. While this can be done for some, there are strict guidelines that restrict the transfer of multiple embryos.

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