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Fresh vs. Frozen Embryo Transfers during IVF

Fresh vs. Frozen Embryo Transfers during IVF
If you’re considering in-vitro fertilization (IVF) to get pregnant, you may have wondered what the differences are between fresh vs. frozen embryo transfers. Knowing the difference can help you make informed decisions, so you have the best possible chance of a healthy and complete pregnancy. Here’s what you need to know about each option and which option is the most successful.

The IVF Process: Choosing the Embryo Transfer Type

The IVF process or cycle is the term used to describe one round of IVF treatment, beginning on the first day of a woman’s period. Depending on the fertility plan, a woman may need to start medication or injections before this day. Here are the steps in the IVF cycle.

Step 1: The First Day of Your Period

Day one is the first official day of your IVF treatment cycle. Since each woman’s body is different, your fertility nurse will help you understand how to identify which day of the month this is for you.

Step 2: Stimulation of Ovaries

In a normal monthly cycle, your ovaries produce a single egg. With the stimulation phase, you will take medication for 8 to 14 days to encourage the follicles in your ovaries to produce multiple eggs. The medication you are prescribed will depend on your specific treatment plan and will be designed to work best with your body. It is usually administered in the form of injections and can vary from one to two injection per cycle or per day.

Your fertility nurse will work with you to ensure that you know exactly how and where to give yourself these injections. Your partner can be involved to help you with these, and you can learn together. Before you know it, this will be come a habit that you are comfortable with.

The most common hormones used in these medications are Follicle-Stimulating Hormone (FSH) and Luteinizing Hormone (LH). These are the same hormones your body naturally makes, but the boost helps you to encourage more eggs to develop.

Your fertility team will keep an eye on your ovaries and how the follicles are developing with blood tests and ultrasounds (some will be transvaginal). If necessary, your medication will be adjusted. More frequent tracking will be done toward the end of the stimulation phase to time the trigger injection perfectly. The trigger injection prepares the eggs for ovulation.

Step 3: Egg Retrieval

After stimulation, your fertility specialist will schedule the egg retrieval before you are set to ovulate. During egg retrieval, a specialist will collect the eggs from your ovaries, which will take about 20-30 minutes.

During the procedure, your specialist will use the latest ultrasound technology to guide a needle into each ovary. They will extract the fluid from the follicles that look like they have grown enough to have an egg inside. They will already have a fair idea from your previous ultrasounds of how many eggs there are before retrieval. In most cases the average number of eggs collected is 8-15.

After this procedure, it will take about 30 minutes for you to recover and to able to walk out on your own. You may want to have a support person with you as you will not be able to drive after the procedure.

Step 4: Sperm Selection

If you are a couple that plans to use fresh sperm, a sperm sample will be collected on the same morning as the egg retrieval. However, if you are using donor sperm or frozen sperm, the specialist will prepare the sample in the lab on that day.

Sperm is typically graded using four levels of quality. It is washed in a special solution to slow it down, so the specialists can spot the best ones under a microscope. Only the best sperm are selected, and they are prepared and ready in the lab to be introduced to the eggs.

Step 5: Fertilization

In the fertilization stage, your specialist take the eggs they retrieved from you, still in the fluid from the follicles, and then using a powerful microscope, they will remove the eggs from the fluid. They will quickly fertilize the eggs using the sperm placed in a dish. The sperm and eggs will have time to find each other and fertilize as they would naturally inside your body.

Step 6: Embryo Development

When sperm fertilizes an egg, it becomes an embryo. Once this happens the specialist will put the embryo into a special incubator for the embryo to grow and develop. These specific growth conditions are made using a mixture of amino acids, just as the body would use to nurture an embryo.

The embryos will be observed over five to six days and then they will be looking for a two- to four-cell embryo on day two and a two- to eight-cell embryo on day three. Implanting embryos at the blastocyst stage into the uterus increases the chances of a successful pregnancy. However, not all eggs will fertilize and reach the embryo stage. If the eggs are not mature enough or if the sperm are not strong enough, the process may not be successful.

Each step of the way you will be kept up to date with the progress of your egg, sperm, and embryo development.

Step 7: Transfer

If your embryo successfully develops in the lab you will be ready for the embryo transfer process into your uterus. Your fertility nurses will contact you to explain what you need to do to prepare for the procedure. It is a simple process, like a pap smear. It should only take about five minutes and you will be awake without any anesthetic. You can get up straight away as there is no downtime.

A specialist will prepare your embryo by placing it in a small tube known as a catheter. Only an expert will do this to minimize any disturbance of the embryo. Your fertility specialist will place the catheter through your cervix and into your uterus where the embryo will implant.

Step 8: Blood Test

About two weeks after your embryo transfer, you will receive a blood test to measure your levels of human Chorionic Gonadotropin (hCG). This hormone signals a positive pregnancy test.

Fresh Embryo Transfers

The Process

After a woman has her eggs retrieved there are two main transfer options: fresh and frozen. For a fresh embryo transfer, the best embryos are transferred to the uterus within three to five days after it was retrieved. The rest of the embryos will be frozen for a future transfer if they are needed.

Success Rates

The Live Birth Rates (LBR) after fresh embryo transfers depend in part on how old the patient is. According to studies, LBR was 36.7% for women under 35 years of age, 26.6% for women 35-37 years of age, 15.6% for women 38-40 years of age, and 9.3% for women 41 and older.

Frozen Embryo Transfers

The Process

With a frozen embryo transfer, all the embryos are immediately frozen after development. When the woman is ready for a transfer, the embryos can be thawed. In many cases, even before the woman’s cycle starts, it may become clear that there needs to be a frozen transfer done. This is especially the case for women who have Polycystic Ovary Syndrome (PCOS) or who want to do a Preimplantation Genetic Test for Aneuploidies (PGT-A).

Success Rates

Studies have shown that LBRs for frozen eggs were 46.7% for women under 35 years of age, 38.6% for women 35-37 years of age, 29.4% for women 38-40 years of age, and 25.9% for women 41 and older. The success rates for frozen embryo transfers are significantly higher for all groups when compared to fresh embryo transfers.

Advantages of Frozen Embryo Transfers over Fresh Embryo Transfers

There are many advantages to frozen embryo transfers over fresh embryo transfers. These include increased implantation rates, increased ongoing pregnancy rates, increased LBRs, decreased miscarriage rates, lowered risk of pre-term labour, and healthier babies.

This may be the case because frozen embryo transfers occur after a woman’s ovaries have been stimulated with hormones and the levels in the body have had time to return to normal. This would mimic a more natural conception process, and therefore, it seems to have a positive impact on the embryo’s health.

IVF and Frozen Embryo Transfers at ONE Fertility Kitchener Waterloo

At ONE Fertility Kitchener Waterloo, we strive to provide our patients with the best medical care and to support their needs as they embark on their fertility journey. We want to end the stigma surrounding IVF treatment and help our patients understand their treatment plan throughout the entire process. Our evidence-based medical approach and compassionate care ensure that each patient receives safe and high-quality fertility treatment.

Contact us at (519) 650-0011 or to learn more about frozen embryo transfers and to find out whether it is right for you. We offer our services to patients from Kitchener-Waterloo, Guelph, Cambridge, Woodstock, Listowel, Fergus, Elmira, Milton, Owen Sound, and other areas of Ontario.


4271 King St East, Suite 200
Kitchener, ON
N2P 2X7

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Saturday-Sunday: 8am-12pm

Contact Us

Phone: 519.650.0011
Fax: 519.650.0033