What is an Embryo Transfer?

The Embryo Transfer

If you are waiting to undergo IVF treatment, then you may be a little worried about exactly what to expect with the procedure. There are many steps involved in the IVF process and it is important to become familiar with each one before you begin the procedure. One of the most important stages of the IVF treatment is the embryo transfer. While this is the final stage of IVF treatment, it is extremely delicate and vital to the success of the entire procedure.

What Is An Embryo Transfer?

Embryo transfer is the IVF procedure where your embryos will be transferred into your uterus. Embryo transfer is completed after your eggs have been fertilized by sperm and the embryos have been cultured. The procedure will be performed at your IVF Clinic.

It is vital that the embryo transfer procedure be performed by a skilled reproductive endocrinologist as mistakes made during the transfer process can affect your chances of pregnancy.

When Is An Embryo Transfer Performed?

Embryo transfer is usually performed once your embryos have been cultured to the right stage. Your eggs will be mixed with sperm and then allowed to develop in a culture medium which will mimic normal human physiology. Following culturing, there are two types of embryo transfers, the choice of which is determined by the Clinic:

Day 3 Embryo Transfer: the Day 3 embryo transfer is performed 72 hours after fertilization.

Day 5 or Blastocyst Transfer: Blastocyst transfer occurs when your embryos have reached the blastocyst stage, five days after fertilization. Some fertility specialists prefer doing blastocyst transfers because it is easier to visualize and choose the healthiest embryos for transfer at this stage.

How Many Embryos Are Transferred?

Generally, between two and four embryos are transferred during each IVF cycle. The exact number of embryos transferred will depend upon a number of factors, including:

· the number of embryos that were formed after egg retrieval,

· the health of your embryos,

· your age, and

· your risk level for multiple pregnancy.

Of course, a greater the number of embryos transferred means a higher risk of a multiple pregnancy. When multiple pregnancies occur the health of both you and your baby are affected, so fertility clinics will modify their procedures to minimize multiple pregnancies. Some countries, such as the UK, will limit the transfers per IVF cycle to two in an attempt to insure a healthy result.

How Is An Embryo Transfer Performed?

Your embryo transfer will be performed at your fertility clinic. It is a completely painless procedure, so you will not receive an anesthetic during the transfer.

You and your partner will be asked to come in a few hours prior to the transfer procedure. You will be asked to drink a lot of fluids to fill your bladder to help your reproductive endocrinologist see more clearly during the ultrasound portion of the transfer. Your embryologist will discuss which embryos are the healthiest to have transferred and how many embryos should be transferred. You and your partner will be able to see pictures of your embryos before the procedure begins.

Once your embryos have been selected, they will be immersed in a fluid and stored in a catheter. You will lie down on an examination table and a speculum inserted into your vagina. Your cervix will be cleaned to prevent interference with placement of the embryos. A flexible catheter will be placed into your cervix to your uterus. The catheter containing your embryos will then be inserted inside of the flexible catheter.

Your physician will perform an ultrasound to determine the best place to deposit your embryos, usually at the very top of your uterus. The embryos will then be pushed out of the catheter and onto your uterine lining.

After The Embryo Transfer

After the transfer has taken place, you will be asked to lie down for two hours. While you may experience some cramping, you shouldn’t experience any other side effects. After two hours, you can go home. It is usually recommended that you take it easy for 48 hours and then you can resume your normal activities.

You may have to give yourself shots of hCG or progesterone, however, this will be determined by your physician. In 12 days, you will return the the IVF Clinic for a blood test to confirm pregnancy.

Remaining Embryos

Most couples have embryos remaining after the IVF process. You and your partner will need to decide what you would like to do with your embryos. There are a number of available options, including cryo-preservation and embryo donation. These options will permit you to store the remaining embryos for your own future use or to help other persons also dealing with infertility. As your Clinic will require you to document your option in the medical file, you should consider them prior to the transfer.

Estrogen and Progesterone Protocol for Embryo Transfer

In a natural cycle the endometrium, or uterine lining, is prepared to support the implantation of an embryo by the hormones estrogen and progesterone. Estrogen is produced by the ovaries and the developing egg in the Follicular Phase of the menstrual cycle and Progesterone is produced by the corpus luteum in the ovary during the Luteal Phase after ovulation. There is a “window of receptivity” after ovulation during which the endometrium is receptive to allowing the embryo to implant. The timing is greatly influenced by exposure to progesterone.

If an embryo transfer is planned for a woman who has not developed and ovulated an egg, the endometrium can be primed for the transfer to occur during this optimum time by giving that woman estrogen and progesterone in a way that mimics a natural cycle. The indications for this type of Estrogen and Progesterone Protocol include:

                Donor Egg Recipients

                Cryopreserved Embryo Transfers with one’s own or Donated Embryos

                Gestational Carriers

In each of these instances the uterine environment is not being controlled by an ovulatory cycle but the endometrium will respond in the same way when exposed to estrogen given orally, transdermally or transvaginally and progesterone usually given by injection. Physicians may choose slightly different protocols but all aim to mimic hormonally what would happen in a natural cycle. The following is one of several protocols.

•          Estrace 1 mg PO BID (twice a day) for 5 days

•          Estrace 2 mg PO BID (twice a day) for 4 days

•          Estrace 3 mg PO TID (three times a day) for 5 days

•          Cycle Day 14 Serum E2, P4 and TV US to check estrogen and progesterone levels and endometrial thickness

•          Cycle Day 15 Estrace 2 mg PO BID (twice a day) for 20 days, until pregnancy test

               Progesterone in Oil 50 mg IM in the evening

•          Cycle Day 16 continue Estrace and start Progesterone  in Oil 100 mg IM every day until pregnancy test

•          Cycle Day 19       Embryo Transfer

If the estrogen levels are not adequate Estrace tablets can be inserted in the vagina rather than taken orally or an estrogen patch like Climara or Vivelle can be used in addition to oral Estrace. If there is a pregnancy Estrace and progesterone will continue generally until 10 weeks at which point the dose may be gradually decreased and then discontinued. Some physicians may use a vaginal form of progesterone such as suppositories, capsules, gel or tablets during the protocol.