What’s the Difference Between a Fresh and Frozen Embryo Transfer?

When choosing between a fresh or frozen embryo transfer during IVF, the right answer might have more to do with your personal circumstances than success rates, here's why...

Is a fresh or frozen transfer better?

A fresh embryo transfer lives up to its name. In this case, it's an egg that has been retrieved, fertilized and transferred back into a woman's uterus all within the time period of about one week.

Frozen embryo transfers, also known as FETs, take a slightly different route. After retrieval and fertilization occur, the embryos are frozen and then stored to be used (or examined) at a later date. Surprisingly, studies show that FETs incur slightly higher pregnancy success rates compared to their fresh embryo counterparts.

IVF Fresh Vs. Frozen Embryo Transfers - Understanding the Difference

In order to qualify as a fresh transfer, ovarian stimulation and embryo transfer must occur during the same cycle. Some clinicians refer to this simply as Embryo Transfer, or ET. Alternatively, doctors can freeze the embryos to preserve them for later implantation, which is commonly called Frozen Embryo Transfer, or FET. While you can opt to freeze all embryos right from the start, FETs frequently take place after a fresh transfer attempt, or in cases which require donated embryo use.

Most clinics will transfer one or two fresh embryos per cycle and freeze the remaining embryos for later use. These frozen embryos can come in handy if no pregnancy occurs following the fresh transfer or if patients seek IVF again in the future for subsequent pregnancies. Some couples or individuals may conceive without assistance following an IVF pregnancy, but others will require IVF to have any and all of their biological children, and so keeping frozen embryos often proves helpful down the line. Once a patient has completed their IVF journey for good, they may choose to donate any remaining embryos.

Many IVF patients begin with a fresh cycle, but some elect to freeze all viable embryos and defer implantation for a later cycle.

During a frozen embryo transfer, frozen embryos are first thawed before being placed into the uterus. The number of embryos used in a frozen cycle depends on what you and your doctor decide together but typically ranges between one and three.

Fresh Embryo Transfers - An Overview

Just like the name suggests, a fresh embryo transfer involves depositing a developing embryo in a patient’s uterus. In order to be considered a fresh transfer, the embryo must never have undergone freezing or thawing. In most cases the transfer will occur just days after the egg retrieval and fertilization phase of the IVF cycle.

Any additional embryos not used for the fresh transfer can be frozen and stored for later use. A reproductive endocrinologist performs the transfer by inserting a thin catheter into the cervix and using a syringe to place the embryo directly into the uterus. This can occur with or without sedation, depending on your doctor’s usual procedure and your individual needs.

Following transfer, most patients find that they can resume usual daily activities. Minor cramping or other discomfort may occur. In addition, the ovaries may still be enlarged following a fresh embryo transfer, which can lead to residual bloating or discomfort. Strenuous activities are typically discouraged following ET.

Reasons why you might want to consider a fresh embryo transfer:

1. Timing – Fresh embryo transfers take less time between stimulation and pregnancy. Many couples and individuals who seek IVF treatment have already spent years trying to conceive by other means. Often by the time patients get to this stage of their fertility journey, they feel understandably anxious to get on with the process. Fresh transfers offer quicker results than frozen, which patients often prefer.
2. (Possibly) Less Expensive – Frozen embryo transfers may have additional costs associated with freezing, storing, or thawing the embryo. Because most women require on average three cycles of IVF to successfully bring home a baby, they will often do anything they can to help save time and funds
3. Embryo Safety – Though IVF has come a long way in recent years, occasionally the freezing and/or thawing process may compromise an embryo. Survival of frozen embryos is currently about 95% according to recent data.<

When a fresh embryo transfer is your only option:

• If You Want to Stim and Transfer in the Same Cycle – If you expect to transfer embryo(s) right away in your first round of IVF (before you have a supply of frozen ones available), then a fresh embryo transfer is the only way to go.

Frozen Embryo Transfers - An Overview

Prior to FET, your doctor will probably prescribe progesterone (or similar hormones) to promote the growth of your uterine lining. The thickness of the lining can influence the embryo’s ability to successfully implant and become a pregnancy. Generally speaking, a thicker lining typically offers a better chance of positive results.

Meanwhile, the embryologists will carefully thaw one or two of your frozen embryos. Out of each step in the FET process, the thawing poses the biggest risk to embryo health, so it should only be performed by skilled specialists. For this reason, and others, it is imperative that you take great care in selecting your fertility clinic

When both the patient and embryo are ready, the reproductive endocrinologist will conduct the transfer using the same procedure as a fresh embryo transfer (see description in “Fresh Embryo Transfers – An Overview” above). Though fresh transfers once dominated the field as the “gold standard” in IVF treatment, emerging evidence now suggests that frozen transfers may actually provide some benefits that increase birth rates, and newborn health compared to fresh transfers.

Reasons why you might want to consider a frozen embryo transfer:

1. Balanced Hormone Levels– Ovarian stimulation can take a toll on patients because of hormonal changes. Frozen transfers give the body time to recover from ovarian stimulation, reducing your chance of OHSS (Ovarian Hyperstimulation Syndrome) and making the body more receptive to pregnancy.
2. Optimal Uterine Lining– Stimulation can sometimes reduce the uterine lining which may prevent implantation. Frozen transfers give the uterus time to restore its lining, optimizing the conditions for a successful implantation and pregnancy.
3. Less Stressful – Patients often find the FET is less stressful than the fresh transfer because they’ve had time to recover from the mental, emotional, and physical impact of the strenuous stimulation phase, and a more relaxed mother may lead to a healthier pregnancy.

When a frozen embryo transfer is your only option:

• When a Fresh Transfer Poses Risk to the Mother – Complications like Ovarian Hyperstimulation Syndrome (OHSS) might make a fresh transfer unsafe. In that case, your doctor will probably advise you to wait for one or more cycles to protect your health
• If You Use a Donated Embryo – Donated embryos always come pre-frozen.
• Once Your Embryos Have Been Frozen – After embryos are frozen, their transfer is considered a frozen transfer (even though they’re always thawed first). So, once your embryos are frozen, there’s no taking them back to fresh (unless you start the whole IVF process all over again from the stimulation phase).

Is a fresh embryo less expensive than a frozen embryo transfer?

As discussed above, frozen transfers may involve additional costs for freezing, storing, and thawing embryos. The exact charges will differ depending on your doctor’s fees, and the fees associated with the storage facility. On average, individual patients do pay more overall when they freeze all embryos rather than starting with a fresh transfer and moving on to their frozen. However, according to recent research the benefits of frozen embryos may increase birth rates enough to off-set the increased cost-per-patient.

Summary

Embryo Transfer is the phase of IVF in which a fertilized egg, which has developed for 3-5 days in a lab, is deposited directly into the uterus.

• Embryos may be transferred quickly following fertilization (Fresh Embryo Transfer or ET), or they may be frozen first and transferred at a later date (Frozen Embryo Transfer or FET).
• Fresh transfers occur in the same IVF cycle as stimulation while frozen transfers take place weeks or months later.
• Fresh transfers offer more immediate results and may cost less overall than frozen transfers.
• Fresh transfers may increase risks associated with OHSS or other IVF related complications.
• Frozen embryos offer a good option for patients whose first transfer does not result in pregnancy.
• Frozen embryos can also be donated and used by couples who need additional reproductive assistance.
• Some patients find frozen transfers less stressful and/or physically strenuous than fresh transfers.
• Frozen transfers may increase IVF success rates, but damage to the embryo can sometimes occur during the freezing or thawing process.

What’s Right for Me?

When choosing between fresh and frozen embryo transfer, there is no one-size-fits all approach. Anyone seeking reproductive assistance should get guidance from their doctor and weigh the pros and cons before making a final decision. Though infertility carries a heavy emotional burden, and we often look for the simplest, easiest, and fastest method of treatment, there are times when the risks associated with fresh transfer simply outweigh the benefit, or vice versa. That’s why it’s so important to understand the procedure for each kind of transfer and follow the advice of your doctor so you can make informed choices about your fertility treatment. Ultimately, no one else can decide which way is best for you.