The timing of the embryo transfer depends on a number of factors including the cell stage of the embryo when frozen and uterine receptivity. It is essential that a Frozen cycle procedure form be completed and returned to the clinic well before the scheduled thaw date.
Frozen Embryo Transfer
This brief, painless procedure involves the doctor placing a catheter that has been loaded with a selected number of embryos by the Embryologist, through the cervix and into the uterus to deposit the embryos. When possible Blastocyst transfers are done, which occur around day five of embryonic growth. Blastocyst transfers allow a more mature embryo to be transferred, allowing the Embryologist to select fewer embryos for transfer, achieving a high pregnancy rate with a lower risk of multiple gestations above twins. Occasionally, cleavage stage, day three of embryonic growth transfer are done at they recommendation of the Embryologist based on the quality of the embryo.
When more eggs are retrieved than needed, we can freeze them for future use (cryopreservation). Embryos can be frozen at any stage between day one and day six after egg retrieval and can be stored for up to five years. We offer frozen embryo transfer at our Valencia, Beverly Hills, and Burbank offices to allow you the chance of conception when the time is right for you.
The frozen embryo transfer process is less invasive than standard egg collection. Frozen embryo transfer can be done during your natural cycle, or we may need to control your cycle with medication depending on whether we can monitor the time of your natural ovulation. The embryos are placed into your uterus at the time of ovulation and the when the thickness of the endometrium (lining of your uterus) is right.
Before the frozen embryo transfer can be performed, your embryos will need to be thawed so the age of the embryos corresponds to the age of your uterine lining. The timing of frozen embryo transfer usually depends on the stage at which the embryos were frozen.
Pretesting for a frozen embryo transfer
In order to maximize the chances for success using frozen embryos, a woman should have a normal uterine cavity. There are three tests that can be used to assess the uterine cavity:
- Hysterosonogram – In which saline is injected into the uterus and the cavity is viewed with ultrasound
- HSG in which x-ray dye is injected into the uterus and the cavity is viewed with x-rays.
- Hysteroscopy – In which a fiberoptic telescope is introduced into the uterus and the cavity is viewed directly.
If abnormalities of the uterine cavity are discovered, they should be corrected surgically before proceeding with a frozen embryo transfer.
The Frozen Embryo Transfer Procedure
The FET procedure is actually fairly straightforward. It is very similar to typical IVF embryo transfer procedures: your body will be monitored for ovulation and endometrial development and then the embryos will be implanted into your uterus.
Estrogen preparation for FET
During a normal menstrual cycle, estrogen is produced by the developing follicle. This estrogen acts on the uterus to thicken and mature the uterine lining. Estrogen is given in a FET cycle for the same reason. There are many different ways that estrogen can be given in a frozen embryo transfer cycle:
- Estrogen pills – Estrace, Premarin
- Estrogen patches – Estraderm, Climera
- Estrogen injections – Delestrogen (estradiol valerate), Depogen (estradiol cypionate)
- Vaginal estrogen – Vagifem, Femring
There is no data that any one method works better than another and a method is usually chosen based on physician preference. We like to use estrogen pills since it is easy to do, inexpensive and very well tolerated.
During the time when estrogen is given, the woman will come to the office periodically to be monitored. A transvaginal ultrasound is performed to determine the thickness of the uterine lining and a blood test is performed to look at the level of estrogen in the blood. On occasion, if the lining is not thickening as it should, the dose or type of estrogen must be increased or prolonged. The length of time the estrogen can be given is very flexible. During this phase, for example, the duration of estrogen may be prolonged to delay the day of embryo transfer to accommodate the patient’s schedule.
The monitoring in a thaw cycle is very flexible. Unlike a fresh IVF cycle during which the required days for monitoring are determined by the growth of the follicles in the ovary, in an FET cycle, the days can be adjusted at any time. Thus, a frozen embryo transfer cycle is much less stressful on the patient.
Before Embryo Transfer
Before your embryos can be thawed and transferred, you and your reproductive endocrinologist need to decide how many embryos to transfer into your uterus. The number of embryos transferred will directly impact the success rate of the FET procedure. Typically, between three and four embryos are transferred during each FET procedure.
Your health care provider will then monitor your body in order to determine the best time for the embryo transfer. You will be given numerous ultrasound scans (probably four or five) in order to monitor follicular development in your ovaries and the thickness of your uterine lining. Your reproductive endocrinologist will try to match the age of your embryos to the correct stage of your menstrual cycle. Typically, embryo transfer takes place about two days after ovulation. Your embryos will be thawed the day before your FET procedure.
The actual transfer of the frozen embryos is painless and straightforward, and only takes about 15 minutes.
- A catheter is inserted through your cervix and into your uterus.
- The embryos are injected into the catheter and deposited in your uterus.
- You will be asked to lie still for a few minutes in order to allow the embryos to settle into your uterine lining.
After the Transfer
After the transfer your reproductive endocrinologist will likely have you continue any fertility medications that you may be using. Twelve days after the FET procedure, you will return to your clinic for a pregnancy test.
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