Pros of a Fresh Transfer

1. Speed to Pregnancy. The biggest advantage of a fresh transfer is time. Your "two-week wait" (the period between transfer and pregnancy test) starts almost immediately after retrieval. If successful, you could be pregnant within 3 weeks of starting your IVF cycle.[5]
   
   
2. Emotional Relief. For many patients, the idea of moving forward without delay provides emotional relief. After months (or years) of fertility treatment, the desire to "just get there" is powerful. A fresh transfer fulfills the need to keep momentum.
   
   
3. Cost Consideration (in some systems). In some insurance or clinic payment structures, a fresh transfer may be included in the base IVF cost, while FET may be an additional charge. However, this varies widely by clinic and location.

Cons of a Fresh Transfer

1. Suboptimal Uterine Environment (The Critical Issue). This is the primary medical reason FET has become preferred. During ovarian stimulation, your body is flooded with high levels of estrogen and progesterone—much higher than in a natural cycle. These elevated hormones cause the endometrium (uterine lining) to advance rapidly, becoming "out of sync" with the embryo's developmental stage.[3]

What this means: By the time your day-5 embryo is ready for transfer, your endometrium may already be on "day 7 or 8" hormonally. This mismatch reduces the "window of implantation" (the brief period when the uterus is receptive). Studies show that in fresh embryo transfer cycles, the endometrium is less receptive compared to FET cycles, where hormone levels are controlled or natural.[6]

2. Risk of Ovarian Hyperstimulation Syndrome (OHSS). OHSS is a potentially serious complication where ovaries become swollen and painful due to overstimulation. Getting pregnant with a fresh transfer can worsen OHSS because pregnancy hormones (hCG) exacerbate the condition. For women at high risk of OHSS (typically those with PCOS or high ovarian response), fresh transfers are contraindicated.[7]
   
   
3. No Option for Preimplantation Genetic Testing (PGT). Preimplantation genetic testing (PGT-A for chromosomal abnormalities, PGT-M for single-gene disorders) requires embryos to be biopsied at the blastocyst stage, then frozen while the cells are sent for genetic analysis. Results take 1-2 weeks. Fresh embryo transfer cycles don't allow time for PGT.[8]

For women over 37 or those with recurrent miscarriage, chromosomal abnormalities (aneuploidy) are a leading cause of IVF failure and miscarriage. Without PGT, you're transferring an embryo without knowing if it's chromosomally normal. FET with PGT significantly improves live birth rates in these populations.[9]

Pros of a Frozen Transfer (FET)

1. Higher Success Rates (The Game-Changer). Multiple large-scale studies show that FET results in higher live birth rates compared to fresh embryo transfer, particularly in certain patient populations.[1][4][11]

Why? The answer is uterine receptivity. When you do FET, your uterus isn't dealing with the high hormone levels from stimulation. The endometrium develops in a controlled, natural-like environment, perfectly synchronized with the embryo. This optimal "window of implantation" means the embryo is more likely to implant successfully.[6]

Example data: A landmark 2018 study published in JAMA found that women undergoing IVF with frozen embryo transfer had a live birth rate of 50% per transfer, compared to 42% with fresh single blastocyst transfer in the same population.[4] Another large randomized trial in NEJM showed that frozen-thawed embryo transfers resulted in higher live birth rates and lower miscarriage rates than fresh transfers.[1]

2. More Natural Uterine Environment. This point bears repeating because it's the biological foundation for why FET works. In a frozen transfer cycle, estrogen and progesterone are administered in controlled doses to mimic a natural cycle's hormonal profile—or, in some cases, a completely natural cycle is used if you ovulate regularly. The result: a receptive endometrium without the "overstimulated" effects that plague fresh cycles.[3]
   
   
3. Allows for Preimplantation Genetic Testing (PGT). FET is the only way to use PGT. The embryo is biopsied on day 5-6, cells are sent for chromosomal analysis, and the embryo is frozen while awaiting results. When results come back, only euploid (chromosomally normal) embryos are transferred.[8]

Why this matters: For women over 35, up to 50-70% of embryos may be aneuploid (abnormal chromosome count). Transferring an aneuploid embryo results in either implantation failure or miscarriage. Using frozen embryos with PGT allows you to select only the embryos with the best chance of a healthy pregnancy.[9]

Studies show that live birth rates in women over 37 increase by 10-20 percentage points when PGT is combined with FET.[12]

4. Nearly Eliminates OHSS Risk. If you're at risk for ovarian hyperstimulation syndrome, FET is the safer choice. By freezing all embryos and avoiding pregnancy in the stimulated cycle, you eliminate the risk of pregnancy worsening OHSS. For high-responders or women with PCOS, this is often the deciding factor.[7]
   
   
5. Flexibility and Family Planning. Frozen embryos can be stored for years (some clinics report successful pregnancies from embryos frozen for 10+ years). This allows you to:

• Take time to recover physically and emotionally from egg retrieval before transfer
• Plan your transfer timing around work, life events, or travel
• Store embryos for future children without repeating ovarian stimulation

6. Cost-Effective Over Time. If your first transfer fails, subsequent FET cycles cost $3,000-$5,000 (medication + monitoring + transfer procedure), compared to $15,000-$25,000 for a full IVF cycle with stimulation. If you have multiple frozen embryos, you can attempt several transfers without the physical and financial burden of repeated stimulation.[13]

Cons of a Frozen Transfer

1. Longer Timeline to Pregnancy. The main drawback of FET is time. You'll wait at least 4-8 weeks between retrieval and transfer—longer if you're doing PGT (results take 1-2 weeks) or if your clinic schedules transfers only on certain days. For patients who have been trying to conceive for years, this delay can feel agonizing.

Perspective: While the wait is real, consider that a failed fresh transfer followed by a repeat IVF cycle takes 2-3 months anyway. FET invests that time upfront for better odds.

2. Very Small Thaw Risk (But Overblown). With older freezing methods (slow-freeze), embryo survival rates after thawing were 80-85%. This caused legitimate concern. With modern vitrification, survival rates exceed 95-98%.[2] The risk of an embryo not surviving thaw is now less than 5%—comparable to the natural attrition rate of embryos in any cycle.

Don't let outdated information scare you. If your clinic uses vitrification (and virtually all do now), this risk is minimal.

3. Potential for Additional Costs. Depending on your clinic and insurance, frozen transfer cycles may incur extra fees for cryopreservation (freezing), storage, and FET cycle monitoring. However, when weighed against the higher success rates and the cost of repeated full IVF cycles after failed fresh transfers, FET is usually more economical long-term.[13]

Key findings from major studies:

1. Ovulatory Women (Normal Ovarian Response): A 2018 study in JAMA (fresh single blastocyst transfer in ovulatory women) found:[4]

• FET live birth rate: 50% per transfer
• Fresh transfer live birth rate: 42% per transfer

2. Women with PCOS: A 2016 NEJM trial showed even larger differences:[1]

• FET live birth rate: 49%
• Fresh transfer live birth rate: 42%
• FET also had lower miscarriage rates (22% vs 32%)

3. Women Using PGT-A: For patients doing preimplantation genetic testing, frozen transfer is mandatory (since embryos must be biopsied and frozen). Studies show that PGT + FET in women over 37 yields live birth rates of 60-65% per euploid embryo transferred—far higher than fresh transfers without PGT.[12]

Why the Difference?

The success advantage of frozen embryo transfer comes down to three factors:

Uterine Receptivity

As explained earlier, the supraphysiologic hormone levels during stimulation make the endometrium advance too quickly, creating an "implantation window" mismatch. FET avoids this problem entirely.[3][6]

Embryo Selection via PGT

When FET is combined with PGT, you're transferring only chromosomally normal embryos, which have much higher implantation and live birth potential.[9]

Embryo Quality Assessment

Extended culture to day 5-7 allows embryologists to observe embryo development more thoroughly before freezing. Only the best-quality embryos are selected for freezing, whereas in fresh cycles, the pressure to transfer "now" sometimes leads to transferring suboptimal embryos.[14]

Are There Cases Where Fresh Is Still Better?

Yes—but they're specific:

1. Poor ovarian responders (few embryos): If you only have 1-2 embryos, some clinics may recommend fresh transfer to avoid the (small) risk of thaw loss. However, even in these cases, FET often still outperforms due to better uterus conditions.[15]
   
   
2. Low OHSS risk + patient preference: If you have a very mild stimulation protocol, normal estrogen levels, and strong preference for immediate transfer, fresh can be reasonable—though success rates may still be slightly lower.

3. Donor egg cycles: In donor egg IVF, the recipient's uterus hasn't undergone stimulation, so there's no hormone-related receptivity issue. In these cases, fresh vs frozen outcomes are equivalent, and the choice is logistical.[16] However, not all patients can undergo menstrual cycle synchronization due to medical reasons. Again, it is worth noting that PGT-A won’t be an option. If the treatment is done abroad, it will result in a longer stay and lower flexibility.

Step 1: Preliminary Testing

Before your FET, your fertility clinic may perform:

• Sonography: A follow-up ultrasound to check for uterine abnormalities (polyps, fibroids)
• Mock transfer: A practice run to map the path to your uterus and ensure no anatomical challenges
• Endometrial receptivity assay (ERA): For patients with repeated implantation failure, this test identifies the exact day when your endometrium is most receptive (personalized implantation window).[17]

Step 2: Uterine Preparation

There are two main protocols for preparing the uterus for FET:

Medicated (Programmed) FET Cycle:

• Estrogen supplementation: You take estrogen (pills, patches, or injections) for 10-14 days to thicken the uterine lining (target: 8mm+).
• Progesterone supplementation: Once the lining is ready, you start progesterone (injections, suppositories, or vaginal gel) to prepare the endometrium for implantation.
• Transfer timing: The embryo is thawed and transferred on a specific day of progesterone exposure (usually day 5 or 6 of progesterone for a day-5 blastocyst).

Natural Cycle FET:

• For women who ovulate regularly, a natural cycle can be monitored with ultrasounds and bloodwork.
• Transfer occurs 5-7 days after natural ovulation, timed to the embryo's stage.
• Some minimal progesterone support may be added after transfer.

Which is better? Both have similar success rates.[18] Medicated cycles offer more scheduling control; natural cycles avoid medications (preferred by some patients).

Step 3: The Transfer Procedure

Embryo thawing happens the morning of transfer. The embryo is loaded into a thin catheter and gently placed into your uterus under ultrasound guidance. The procedure takes 5-10 minutes and is painless (no anesthesia needed).

Step 4: The Two-Week Wait

After transfer, you continue progesterone supplementation for 10-12 weeks if pregnancy occurs. Pregnancy test (blood hCG) is typically done 9-11 days after transfer.

A Frozen Transfer is recommended if:

✓ You want the highest possible live birth rate

✓ You wish to do preimplantation genetic testing (PGT)

✓ You are at risk for OHSS (high estrogen, PCOS, high responder)

✓ You are over 35 (where PGT significantly improves outcomes)

✓ You have a history of recurrent miscarriage or repeated implantation failure

✓ You plan to have multiple children and want to bank embryos for future use

✓ You prioritize evidence-based fertility treatment over speed

In practice, most IVF patients today undergo FET as the standard of care.