Frozen Embryo Transfer
Bay IVF - Advanced Reproductive Care                                Palo Alto  650-322-0500


Frozen (Cryopreserved, Vitrified) Embryo Transfer

In Vitro Fertilization, Donor Egg IVF, and Frozen Donor Egg IVF treatments can result in the creation of more embryos than you may wish to have transferred. It is typically possible to cryopreserve (vitrify) these extra embryos and store them for any length of time in liquid nitrogen. The stored embryos can be thawed and transferred into the uterus at a later date.

We will let you know whether your remaining embryos are of high enough quality for cryopreservation. Embryo cryopreservation and storage are done on-site.

The complexity and cost of a Frozen Embryo Transfer are less than repeating a "fresh" cycle of treatment. A large majority of vitrified embryos will survive the vitrification and thawing process. The implantation rate of the thawed embryos is equal to the "fresh" embryo implantation rate.

Please give us a call when you decide to have your embryos thawed and transferred.

Frozen Embryo Transfer procedure consists of:

  1. Preparation of endometrial lining
  2. Thawing and culture of cryopreserved embryos
  3. Assisted embryo hatching
  4. Embryo transfer
  5. Implantation


  1. Preparation of Endometrial Lining

    There are several different forms of endometrial lining stimulation protocols, each with many modifications. Your treatment is always individualized.

    Below is an example of endometrial stimulation protocols used at Bay IVF. Your cryopreserved embryo transfer cycle may take less or more time to complete.

Endometrial Stimulation Example


Endometrial Stimulation Example


The treatment begins by taking oral contraceptives. They are started within the first four days of the beginning of a menstrual cycle. A few days after the last pill, you will have a menstrual period, and the endometrial stimulation will begin at that time.

Oral and injectable medications are used to prepare your endometrial lining for the transfer of frozen-thawed embryos. The endometrial lining preparation is straightforward, and you should not expect any side effects.

  1. Thawing and Culture of Cryopreserved Embryos

    You will need to decide and communicate to us how many vitrified/thawed embryos you would like to transfer. Please let us know if you need help with this decision.

    Most patients should select one or two embryos for the thaw and transfer to eliminate the risk of a high order multiple pregnancy (triplets or more). With this approach, most pregnancies from cryopreserved embryos are single baby pregnancies.

  2. Assisted Hatching

    Assisted hatching is a laboratory procedure used to create a "weak spot" in the eggshell of an embryo. Since embryo freezing commonly hardens the embryo eggshell, assisted embryo hatching is always a part of the Frozen Embryo Transfer treatment.

    This picture shows an embryo after assisted embryo hatching with an opening breaching the eggshell at the 12 o’clock position.


Assisted Hatching


  1. Embryo Transfer

    Transfer of cryopreserved embryos into the uterus is identical to "fresh" embryo transfer: Just prior to the embryo transfer, the embryos are placed into the tip of a thin embryo transfer catheter. The catheter is then passed through the cervical canal to within 15 mm of the top of the uterine cavity, and the embryos are gently released.

  2. Implantation

    After the embryo transfer, the endometrial lining gently holds the embryo(s) at the top of the uterus. There is no restriction on your physical activity.

    A blood pregnancy test is done ten days after the embryo transfer. If the pregnancy test is positive, an ultrasound examination is scheduled two weeks later to visualize the implantation site and to look for a heartbeat within the embryo. Once a heartbeat is seen, there is a 95% probability that the pregnancy will continue to a baby.

    There is no increased risk of birth defects in pregnancies from cryopreserved embryos compared with conceptions conceived through intercourse or using "fresh" embryos.

    Supplementation of estrogen and progesterone must continue until the placenta produces enough of its own estrogen and progesterone to sustain the pregnancy. You will be closely monitored for 6 to 8 weeks as this transition takes place. Once all medications are discontinued, you will be referred to your OB doctor for the remainder of your obstetrical care.

    At this point, your pregnancy becomes indistinguishable from conception through intercourse, and your obstetrical care should be no different than if you conceived without any treatment.


Please use the following links for information about reproductive treatments at Bay IVF and to request a consultation.


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