Mock Embryo Transfer Procedure

Mock embryo transfer is a common procedure done at most fertility clinics. The actual embryo transfer occurs in the middle of your IVF cycle, while the mock embryo transfer may occur before or during your IVF cycle.

A difficult embryo transfer has been associated with lower pregnancy success rates. A mock embryo transfer—which gives your doctor the opportunity to perfect the technique needed to do your actual transfer—may increase your chances of getting pregnant. The super-short run down of IVF treatment goes like this:

1. The pre-IVF cycle (where you usually are on birth control pills, GnRH Agonists, or some other medication to “shut down” your reproductive cycle)
2. Ovulation stimulation (where you’re injecting gonadotropins to boost follicle growth and production, and having multiple ultrasounds and blood work to monitor that growth)
3. The egg retrieval (where the matured eggs are removed from the ovaries via needle aspiration),
4. And then, finally, a few days after the retrieval, the embryo transfer (where the fertilized eggs are transferred to your uterus or a surrogate’s uterus)

The “mock” embryo transfer is a trial run of the actual embryo transfer. It allows the doctor to determine the best “route” to the ideal embryo landing place in your uterus, to measure the length from cervix to that ideal place, and ensure that there are no unexpected road bumps along the way (like an undetected fibroid, scar tissue on the cervix, or other problem that may make transfer difficult).

Embryo transfer may look like it should be the simplest procedure in the IVF cycle, but if it’s done incorrectly, the entire cycle can be lost. There’s some disagreement among doctors on when and whether to do a mock embryo transfer, but for now, the majority of fertility doctors agree it’s best to have one.

Timing of Mock Transfers

This will depend on your doctor’s preference and does not impact implantation rates. The mock embryo transfer may take place:

• More than a month before the actual IVF cycle, during an HSG, saline hysterography, or hysteroscopy
• The month before your actual IVF cycle, usually when the reproductive system is being quieted down with birth control pills or Lupron (This seems to be the most common time for the mock embryo transfer.)
• During the egg retrieval. In this case, you won’t even know it happened since you’ll be under anesthesia. 
• On the same day as the actual embryo transfer. First, the doctor does the mock transfer, and then right away, the actual transfer.

What to Expect

You will probably be told to come to the procedure with a full bladder. This is for two reasons:

• Your full bladder pushes the uterus into a different alignment, which makes the transfer easier.
• A full bladder helps with the ultrasound picture quality. 

You’ll be asked to lie on your back, with your feet in stir-ups, much like a pap smear or regular gynecological exam. A speculum will be used to help your doctor place the catheter into and through the cervix into your uterus. Your doctor’s goals during the mock embryo transfer may include:

• Choosing the best catheter to use with your particular anatomy
• Making sure there are no “speed bumps” to prevent the catheter from entering the cervix smoothly
• Figuring out the best path from the cervix to the transfer area in the uterus, which may vary according to the position of the uterus
• Measuring the distance from the cervical opening to the perfect transfer spot in the uterus

There won't be any embryos on the catheter during the mock transfer. Your doctor may also inject a blue dye during the mock transfer. After the catheter is removed, your doctor will ensure there’s no blue dye remaining on the tip of the catheter or at the entrance to your cervix. 

Will a Transfer Hurt?

You may feel cramping or a sharp but tolerable pain when the catheter is placed, especially if your doctor needs to move it around a lot to find the right placement, or if your doctor has difficulty passing the catheter through the cervical os. 

Some women only feel slight discomfort like during a pap smear, and nothing more. If your doctor accidentally hits the fundus of your uterus (basically the back wall), you may experience a strong cramping sensation.

If the mock embryo transfer is done during your egg retrieval, you’ll be under anesthesia and won’t feel a thing. You may experience some mild cramps the day of the procedure, but it’s nothing that should keep you from going about your normal day.

Potential Risks and Cost

A mock embryo transfer is a very low risk procedure. As with the regular embryo transfer, there is a very rare chance of developing an infection.

If you develop a fever within a few days of the procedure, experience severe cramping, or unusual bleeding (not just spotting), be sure to contact your doctor.

The fee may be wrapped up in an “IVF package” or bundled together with the actual embryo transfer or egg retrieval.

Why Mock Transfers Are Done

The embryo transfer requires taking the embryos into a catheter and then transferring them to the uterus via the cervix. It may seem like a simple procedure, especially when you compare it to the egg retrieval or even the ovulation stimulation period of the cycle. However, it turns out the procedure is more complicated than it appears.

Also, if the transfer is difficult, and your doctor needs to manipulate the uterus a great deal in order to get the catheter to the right place, or the catheter touches the fundus of the uterus, it can cause uterine contractions. These contractions may cause the embryos to be expelled.

One study with over 4,000 embryo transfers looked to see if having a more difficult time with the embryo transfer affected pregnancy rates. It did. When compared to the difficult transfers, there were 1.7 times as many pregnancies in women who had an “easy” or “intermediate” embryo transfer.

But can a mock embryo transfer improve your odds of the actual transfer going smoothly? That’s a matter of debate.

One of the arguments against mock transfers is that they are frequently done before the IVF cycle begins, before ovarian stimulation begins. The stimulated ovaries alter the position and "distances" of the uterus. So the measurements that worked when you weren’t stimulated with fertility drugs may be different.

Future research will hopefully look at whether mock embryo transfers can really help the actual embryo transfer go smoothly or not, and when would be the best time to do them. For now, your doctor’s personal preference will determine when and whether you’ll have a mock embryo transfer.