EGG THAW & FERTILIZATION
EGG THAW AND EMBRYO TRANSFER CYCLE
When a woman is ready to use the cryopreserved eggs she has in storage - either from a fresh stimulation cycle she completed or from an egg donor/egg bank - she will contact TFC to start planning the thaw and embryo transfer cycle.
During the consultation you will discuss: the number of frozen eggs available, the recommended number of eggs to thaw and embryos to transfer, and how the uterine lining is prepared to accept the embryos. For your convenience, an appointment with our IVF Coordinator, Laura Troche, can follow the consultation to plan the cycle.
Steps in an Egg Thaw and Embryo Transfer Cycle:
The development of an optimal uterine lining (endometrium) in which the embryo can implant is a crucial step in the cycle. At TFC we use a medically programmed treatment plan to achieve this goal.
The woman takes birth control pills for 2-4 weeks to quiet the ovaries. When instructed, the pills are stopped and the woman begins daily oral Estrace tablets to stimulate the growth of the uterine lining. After 2 weeks of medication, a blood test (for estradiol level) and an ultrasound of the uterine lining are performed to ensure an adequate endometrial thickness is developing before the eggs are thawed and embryos created. Five days prior to the embryo transfer, progesterone is started to make the endometrium receptive to the embryo(s).
The thawing of vitrified (frozen) eggs is a very quick procedure. The designated number of frozen eggs to thaw are removed from cryostorage and rapidly thawed using the required warming solutions. Sperm, provided by the partner or a donor, must undergo biochemical and structural changes called capacitation before it can fertilize an egg.
After the eggs are thawed, the embryologist using a microscope, captures a sperm in a very thin glass pipette and inserts it directly into the egg. This technique of injecting an individual sperm into each mature egg is called Intracytoplasmic Sperm Injection (ICSI)
Approximately 16 hours following sperm injection, the eggs are inspected under the microscope to determine how many have fertilized. These embryos (fertilized eggs) will remain in the incubator as they continue to grow and develop until the moment of transfer.
The woman receives regular reports keeping her informed of the development of the embryos (number of eggs thawed and fertilized, cell division and quality or grading of the embryos). Generally, at 2 days normal embryos are 4 cells, at 3 days they are 8 cells, and at 5 days they have over 80 cells with an inner fluid-filled cavity and a small cluster of cells called an inner cell mass (blastocyst stage). The decision of when to perform the embryo transfer is based on the number and grading of the embryos.
At TFC, we plan for an embryo transfer on day 5 or at the blastocyst stage of embryo development. Blastocysts have a higher implantation rate than embryos incubated only 3 days.
Three days after ICSI, the embryologist will evaluate the embryos for their quality and provide a grade. If there are at least 2 grade “A” or good quality embryos, blastocyst transfer is confirmed and the embryos remain in culture to develop further. At day 5 the best looking blastocyst stage embryo or embryos are transferred into the woman’s uterus. If there are not 2 grade “A” embryos, a day 3 embryo transfer is planned. Any viable, good quality embryos not transferred into the woman’s uterus may be cryopreserved for future use if the individual/couple wishes.
With the goal of decreasing the incidence of multiple births (twins or triplets) TFC utilizes the American Society of Reproductive Medicine (ASRM) guidelines for the number of embryos to transfer. Using the information about the embryo number and quality, and mindful of the ASRM recommendations, the physician and woman/couple will determine the number of embryos to transfer.
Assisted Hatching is a common laboratory technique in which an embryologist uses a precise laser to make an opening in the shell of the embryo to facilitate implantation by the embryo. The hatching is performed immediately before loading the embryo into the transfer catheter. It is recommended if embryo quality is less than optimal, for all Frozen Embryo Transfer (FET) cycles, and cycles where cryopreserved eggs are used.
All embryo transfers are performed using ultrasound guidance as it allows for accurate placement of the embryos in the optimal location in the uterus. The embryo is transferred via a thin plastic tube (catheter) which is carefully guided into the upper part of the uterus and the embryo is placed. The transfer is a painless procedure and the woman remains resting for 30 minutes, after which she goes home. We recommend she rests at home through the next day before resuming her activities.
After the Embryo Transfer
Progesterone supplementation (vaginal gel or IM injections and suppositories) is used to enhance implantation of the embryo and support an early pregnancy. Fifteen days following the egg thawing and ICSI procedure a pregnancy test is performed. If the test is positive, ultrasound confirmation of a clinical pregnancy (presence of heart beat) is performed about 3 weeks later. The progesterone supplementation continue until the pregnancy can sustain itself at 12 weeks.