Frozen Embryo Transfer (FET): A Detailed Guide

A frozen embryo transfer (FET) is one of the most important steps in the IVF process for many. It is the moment when an embryo, created and frozen in an IVF cycle, is thawed and gently placed into the uterus, where it can implant and grow. 

While fresh transfers were once the standard, frozen transfers have become increasingly common thanks to advances in embryo freezing technology (vitrification) and their flexibility for patients. Today, many patients and fertility specialists choose FETs for medical, logistical, and personal reasons. 

This article will explain why FETs are so widely used, what they cost, and how you can prepare for the best possible outcome. 

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Fast Facts About Frozen Embryo Transfers (FETs) 

• What it is: A frozen embryo transfer (FET) is the process of thawing a previously frozen embryo and gently placing it into the uterus for implantation. 
• Why it’s done: FETs are often chosen when the uterine environment isn’t ready for a fresh transfer, to give the body time to recover, or to use embryos saved for the future. 
• Medicated vs Natural: Most FETs are medicated, using estrogen and progesterone to prepare the uterine lining. Natural FETs rely on a woman’s own ovulation cycle, sometimes with light medical supplementation. 
• Success rates: With modern freezing techniques (vitrification), FET success rates are comparable to fresh transfers. In some cases, outcomes are even better due to improved uterine receptivity. 
• Cost: The average cost of an FET in the U.S. is around $5,000. At CNY Fertility, FETs start at $945. Medications for a medicated cycle can add around $500. 
• Preparation: Lifestyle and nutritional changes made 30–90 days before stimulation, such as fertility supplements, diet adjustments, and acupuncture, can support egg and uterine health and improve success rates. 
• Alternatives: Frozen embryo transfers are one of two types of embryo transfers – the other being a fresh embryo transfer.

Why Choose a Frozen Embryo Transfer? 

There are three primary reasons why patients may opt for a frozen embryo transfer.  

Medically Advised 

During an IVF cycle, the ovaries are stimulated with medications to produce multiple eggs. This process places the body under significant physiological stress.

Sometimes, the uterus is not ready to receive an embryo just a few days later. When this happens, it is medically advised to delay the transfer and instead freeze the embryos for use in a later cycle.

By waiting, the uterus has more time to recover and become optimally receptive to an embryo. 

Easier to Plan 

Frozen embryo transfers are rarely canceled once the cycle has started. This makes them much easier to plan, especially for patients who are traveling for treatment.

Scheduling is more flexible, cycles can be arranged in advance, and success rates are comparable to fresh transfers.

Making Use of Remaining Embryos 

A typical IVF cycle can produce multiple high-quality embryos.

Today’s standard of care is to transfer one embryo at a time and freeze the remaining embryos for future use.

FETs make it possible to attempt pregnancy again after a failed transfer or to return later to expand your family, all without undergoing another full IVF stimulation and retrieval cycle. 

FET Medication Protocols

Most frozen embryo transfers are done as medicated cycles, but natural options exist as well. 

Medicated FET: In a medicated frozen embryo transfer, your uterine lining is prepared using estrogen and progesterone rather than your body’s natural hormones.

This approach enables precise cycle control and scheduling, making it particularly beneficial for patients with irregular periods or those who struggle to establish a sufficient lining.

Medicated FETs are often preferred for their predictability, convenience, and overall effectiveness.

Natural FET: In a natural frozen embryo transfer, your body’s own ovulation determines the timing of the procedure.

Rather than relying on estrogen to prepare the lining, your uterus develops naturally, and your body produces its own progesterone after ovulation.

Natural FETs are generally best suited for patients with regular menstrual cycles and predictable ovulation patterns.

Modified Natural FET: A modified natural frozen embryo transfer blends the benefits of both natural and medicated approaches.

Your natural cycle remains the foundation, but medications such as letrozole or an hCG trigger shot may be used to precisely time ovulation and optimize the transfer window.

This method offers a balance between the simplicity of a natural cycle and the flexibility and control of a medicated one—reducing the overall medication load while maintaining consistent, predictable timing.

All approaches can be effective. Your clinical care team will guide whether a medicated, natural, or modified natural FET protocol is appropriate for your body and treatment plan.

Frozen Embryo Transfer Timeline

In a medicated frozen embryo transfer cycle, hormone medications are used to create the ideal environment for implantation. The two main medications are: 

• Estrogen: Taken orally, vaginally, or via patches to thicken the uterine lining. Estrogen is usually started on day 2–4 of your menstrual cycle. 
• Progesterone: Taken as vaginal suppositories, oral pills, or intramuscular injections (progesterone in oil). Progesterone makes the uterine lining receptive to the embryo and is typically started three days before a cleavage-stage transfer or five days before a blastocyst transfer. 

FET timeline at a glance

• Day 1–2 of cycle: Begin estrogen.
• Day 10–14: Monitoring via ultrasound and bloodwork checks lining thickness.
• 3–5 days before transfer: Begin progesterone, depending on embryo stage.
• Transfer day: Embryo is thawed and gently placed into the uterus.
• After transfer: Progesterone continues through the luteal phase and into early pregnancy to support implantation. 

When to stop progesterone after frozen embryo transfer? 

When it comes to the question of when to stop progesterone after a frozen embryo transfer, most clinics recommend continuing progesterone until the placenta takes over hormone production.

This usually happens between 8 and 12 weeks of pregnancy. The exact timing varies by clinic and patient, so it’s important to follow your fertility specialist’s instructions closely. 

Stopping too early may compromise early pregnancy support, while continuing too long generally poses no harm. 

What is a good progesterone level for frozen embryo transfer?

According to the most up-to-date research, a “good” progesterone level for a frozen embryo transfer falls somewhere between 10-20 ng/mL on the day of transfer in many medicated FET protocols.

Levels under ~10 ng/mL often correlate with reduced pregnancy rates. Levels far above ~30-32 ng/mL have been linked in some studies to worse outcomes.

Because individual response, endometrial preparation, embryo stage, and the way that progesterone is administered matter, your fertility specialist will tailor this target range to your specific situation.

Cost of a Frozen Embryo Transfer 

The cost of a frozen embryo transfer can vary significantly between clinics.

Nationwide, the average cost is around $5,000, but it ranges widely. Here at CNY Fertility, an FET starts at $945 (including the procedure and monitoring) to over $7,000 at other clinics. 

Medication costs are an additional consideration. For medicated cycles, estrogen, progesterone, and other medications typically add around $500. 

At CNY Fertility, our goal is to keep treatment as accessible as possible by offering some of the most affordable FET pricing in the country. 

To learn more about IVF with a frozen embryo transfer at CNY, schedule a consultation and explore our cost calculator below. 

Preparing for a Frozen Embryo Transfer 

The groundwork for a successful transfer often starts months before the procedure itself. Eggs begin their final stage of development about 90 days before ovulation, so lifestyle and nutritional changes made in that window can strengthen egg quality and improve outcomes. 

Diet and Supplementation 

Nutrition: A high-fat, low-carb diet may help reduce inflammation, support gut and reproductive health, and stabilize hormone function. 

Supplements: Over-the-counter supplements such as CoQ10 (ubiquinol), inositol, and vitamin D have been shown to support fertility. At CNY Fertility, we often recommend comprehensive fertility supplements such as our own Ovarian Bloom, Peak Prenatal, and VivoMega Fish Oil for women, and Male Preconception+ for men to optimize sperm health. 

Acupuncture 

Research suggests that acupuncture performed both before and after embryo transfer can improve outcomes. Fourteen studies published in Fertility and Sterility found that acupuncture increased pregnancy rates by up to 35–50% when performed around the time of transfer. 

What to Expect During a FET Cycle 

In a frozen embryo transfer cycle:

• The uterus is prepared with estrogen and progesterone medications (if medicated) to prime the endometrium. Bloodwork and ultrasounds are used to monitor hormone levels and ensure the uterine lining is receptive. 
• Once the endometrium is ready, the embryo is thawed, carefully loaded into a thin catheter, and transferred into the uterus under ultrasound guidance. The procedure is quick and usually painless, though a mild relaxant may be offered. 

Frozen Embryo Transfer: The Bottom Line 

A frozen embryo transfer is a powerful tool for achieving pregnancy, offering flexibility, excellent success rates, and multiple chances at pregnancy from a single IVF cycle.

Whether through a medicated or natural approach, FETs can be tailored to your unique needs. 

At CNY Fertility, we work closely with each patient to determine the right timing and protocol for their transfer. With preparation, guidance, and support, an FET can bring you one step closer to building the family you’ve been dreaming of.