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Posted on 04/10/2020 in Fertility Treatment Options

Mock Embryo Transfer: What to expect?

Mock Embryo Transfer: What to expect?

In vitro fertilization (IVF) involves many procedures which prepare you for the actual transfer of the embryo. Embryo transfer is a blind procedure and some difficulties can unexpectedly arise. Therefore, many IVF programmes perform a ‘mock’ embryo transfer. It is done prior to the treatment cycle to determine the most suitable catheter and technique for actual embryo transfer. Moreover, as the uterus is mobile, its direction may vary on the day of the embryo transfer from what it was during the mock embryo transfer. Performing mock embryo transfer immediately before the real transfer can show these problems.


In the middle of your cycle, your doctor will do a mock embryo transfer. It is a trial of the actual embryo transfer. The actual embryo transfer requires taking the embryos into a catheter and then transferring them to the uterus via the cervix. This procedure is more complicated than it appears. It’s not enough to just drop those tiny embryos anywhere inside the uterus. There is an ideal area in your uterus where they should be accurately placed.

Your doctor takes a catheter and essentially pretends to transfer an embryo into your uterus, while a nurse does an ultrasound and takes pictures to see where she is going. She will take measurements, and basically make himself/herself a little ‘map’ of your uterus, so when he/she has got your precious tiny embryo or embryos, he/she knows exactly where to go, and can be in and out. You should have a full bladder for this procedure.

(2) Why should you sign the papers and do a mock embryo transfer? 

Mock embryo transfer is done to collect valuable information for when the actual embryo transfer takes place. It will help your doctor establish where the embryo will go and where the embryo should be placed before the actual embryo transfer will happen. Knowing the length of the uterine cavity, its orientation and, how easy it is to pass the endocervical canal should help your doctor in doing an easy embryo transfer when the time comes. This information allows your doctor to determine the best route to place the embryo within your uterus. It is also used to assess for unexpected difficulties such as undetected fibroids, scar tissue on the cervix, or any other problem that may make actual embryo transfer complicated.

(3) Why should your doctor perform a mock embryo transfer prior to actual embryo transfer? 

During IVF treatment cycle, the embryo transfer is a critical final procedure. Embryo transfer is a simple non–surgical intervention. But the smooth performance of embryo transfer dramatically impacts the outcome of IVF treatment. The success of the actual embryo transfer depends on the mock embryo transfer performance.

Even though the transfer technique is basically simple, unexpected difficulties can be encountered during the transfer procedure. The mock embryo transfer helps your doctor to ‘make a map’ of your uterus [ultrasound scans], to know what may complicate the procedure, the positioning of the catheter (as sometimes mispositioning of the catheter may occur), the presence or absence of blood on the catheter, bacterial contamination of the catheter and the type of catheter should be used for the embryo transfer. A trial or mock embryo transfer is commonly practiced to assess uterine depth and position, in preparation for an optimal real embryo transfer. All mock and real embryo transfers are performed under abdominal ultrasound guidance.

(4) If I don’t want it and say: ‘NO’. What may happen if you say ‘NO’ to a mock embryo transfer performance? 

The technique of embryo transfer is very crucial and great attention and time should be given to this step. To optimize the embryo transfer technique, and to prevent the complications during the embryo transfer, several precautions should be taken. And all the above–mentioned will be possible ONLY if the mock transfer is performed.

The first and most important is to avoid the initiation of uterine contractility. This can be achieved by the use of soft catheters, gentle manipulation and by avoiding touching the fundus. That means that your doctor should not only know all the anatomy of your uterine cavity and the uterus via ultrasound scans but should have a ‘HANDS–ON TRAINING’ to choose the most flexible embryo transfer catheter and the unique technique for embryo transfer.

Secondly, proper evaluation of the uterine cavity and utero–cervical angulation is very important. By performing mock embryo transfer and by ultrasound evaluation of the utero–cervical angulation, and uterine cavity length, your doctor understands what he should do when the time of the actual embryo transfer comes.

Another important step is the removal of cervical mucus so that it does not stick to the catheter and inadvertently remove the embryo during catheter withdrawal. Finally, one has to be absolutely sure that the embryo transfer catheter has passed the internal cervical os and that the embryos are delivered gently inside the uterine cavity.

Embryo transfer is basically a blind technique, associated with multiple potential negative factors that can result in total failure of the whole procedure. These potential negative factors include: (1) initiation of uterine contractility that may lead to an immediate or delayed expulsion of the embryos; (2) the presence of cervical mucus that can plug the tip of the catheter or entangle the embryos and drag them out during withdrawal of the catheter; (3) proper placement of the embryos into the uterine cavity may not be achieved due to failure to pass the catheter through the internal os. This can be due to acute utero–cervical angulation, cervical stenosis or anatomical distortion of the cervical canal. A MOCK EMBRYO TRANSFER REDUCES THE RISKS OF EMBRYO TRANSFER FAILURE as it shows your doctor what may happen during the actual procedure.

(5) How is a mock embryo transfer performed? What to expect? The ‘Glance inside’ this procedure

Probably, your doctor will tell you to come to the procedure with a full bladder. Why should you come with a full bladder? There are two reasons for that. The full bladder pushes the uterus into a different alignment, which makes the transfer easier. The full bladder helps your doctor to see the ‘TRAJECTORY’ of the catheter placed in the uterus via ultrasound imaging.

During a mock transfer procedure, no embryo is transferred to your uterus. The doctor introduces a small catheter guided by the ultrasound imaging into the uterus through the cervix.

This procedure helps your doctor (1) to note down some suggestions for optimizing the embryo transfer technique, (2) to evaluate your anatomy (the cervix uteri, the uterine position, the uterine cavity, etc.), (3) to evaluate the length and direction of the uterine cavity and cervical canal, (4) to choose the most suitable catheter for the embryo transfer, (5) to ‘feel’ the way along the cervical and endometrial canal while threading the embryo transfer catheter, and to visualize the uterine position for the embryo transfer, (6) to figure out the best ‘way’ from the cervix to the transfer area in the uterus, which may vary according to the position of the uterus, (7) to measure the distance from the cervical opening to the perfect transfer spot in the uterus, (8) to discover any unanticipated difficulty in entering the uterine cavity, such as pin–point external os, the presence of cervical polypi or fibroids, and anatomical distortion of the cervix from previous surgery or due to congenital anomalies.

Your doctor will also make some ultrasound scan images, which will help when the embryo is actually transferred. These are the ‘visible reminders’ that will help your doctor determine the optimal position in which to insert the embryo later on. The whole procedure should take no more than about 15 to 20 minutes.

(6) What may happen before the EMBRYO TRANSFER? 

The uterine position may vary between mock and real embryo transfer, possibly because of the enlarged stimulated ovaries. The enlarged ovaries may cause a change in uterine position between mock and real embryo transfer because they push the uterus, and the uterus may ‘reposition’ itself. Therefore, during the mock embryo transfer, your doctor will not only write down some notes about your Uterine position and endometrial cavity depth but also some notes about the possible changes.

(7) Is there the exact optimal time for a mock embryo transfer? 

There is no exact timeline for performing a mock embryo transfer. The time depends on your doctor’s preference. The mock embryo transfer may take place:

(1) More than one month before the actual IVF cycle, during an HSG, saline hysterography, or hysteroscopy.

(2) The month before your actual IVF cycle, when you are taking birth control pills or Lupron.

(3) During the oocyte [egg] retrieval (you won’t feel it since you will be under anesthesia).

(4) On the same day as the actual embryo transfer. First, the doctor does the mock transfer, and then the embryo transfer.

(8) Will a mock embryo transfer hurt?

The stimulus of the transfer catheter passing through the internal cervical os can initiate uterine contractions. You may feel cramping or a sharp but tolerable pain when the catheter is placed in your uterus. Especially if your doctor has difficulty passing the catheter through the cervical os. Or if your doctor needs to move it around a lot to find the right way through the cervical os. If your doctor accidentally hits the fundus of your uterus, you may feel strong cramping. If the mock embryo transfer is done during your egg retrieval, you will be under anesthesia and you won’t feel it. You may feel the mild cramps after the procedure (during this day).

A gentle direction of the catheter following the contour of the endometrial cavity is essential to avoid disrupting the endometrium and eliciting deleterious uterine contractions, which may expel the embryo. The accurate knowledge of the uterine angle at the time of embryo transfer will help your doctor with a smooth single motion passage of the embryo transfer catheter. Therefore, a mock transfer is an essential procedure which should be performed before the actual embryo transfer.

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