Fresh vs Frozen Embryo Transfer: Which Is Better?
Complete comparison of fresh and frozen embryo transfer (FET). Success rates, costs, timeline, pros/cons, who should freeze-all, and how to choose between approaches.
Which is better: fresh or frozen embryo transfer?
FET has equal or slightly higher success rates for most patients (40-50% vs 35-45% for fresh in women under 35). Freeze-all is mandatory for PCOS, OHSS risk, or PGT-A testing.
How much does FET cost?
£1,500-2,500 (UK) or $3,000-5,000 (USA) per transfer, plus £500-800 for initial freezing and £200-350/year storage. Total: £2,200-3,800 per FET.
How long to wait for FET after egg retrieval?
4-8 weeks (1-2 menstrual cycles) to allow ovaries to recover and hormones to normalise. Improves uterine receptivity and success rates.
Key Takeaway: Frozen embryo transfer (FET) now equals or exceeds fresh transfer success rates for most patients (40-50% vs 35-45% for women under 35). FET allows uterine recovery from stimulation hormones, improving receptivity. Freeze-all is mandatory for OHSS risk, PCOS, PGT-A testing, or elevated progesterone. Fresh transfer is still good option if hormone levels normal and no complications. FET costs £1,500-2,500 extra and adds 4-8 weeks to timeline. Modern vitrification has 95-99% embryo survival. Choice depends on individual factors—discuss with your RE.
Table of Contents
Fresh vs Frozen: What's the Difference?
Fresh Embryo Transfer
- •Transfer occurs 3-5 days after egg retrieval
- •Same IVF cycle—no interruption
- •Your body still recovering from stimulation
- •High hormone levels (oestrogen, progesterone)
- •No embryo freezing costs
- •Faster path to pregnancy (if successful)
Frozen Embryo Transfer (FET)
- •Transfer 4-8 weeks (or more) after egg retrieval
- •Separate cycle—pause after egg retrieval
- •Body fully recovered, hormones normalised
- •Natural or hormone-replacement cycle
- •Additional costs (£1,500-2,500)
- •Better uterine receptivity often
The Freeze-All Revolution
A decade ago, fresh transfer was standard and frozen transfer was backup for leftover embryos. But modern research shows FET often equals or surpasses fresh transfer success rates. This led to the "freeze-all" approach—intentionally freezing all embryos and doing FET later, even when fresh transfer is medically possible.
Why the shift? Advances in vitrification (flash-freezing) technology now achieve 95-99% embryo survival rates, making freezing essentially "risk-free." Meanwhile, research revealed that ovarian stimulation hormones can impair uterine receptivity, making the "recovered" uterus better for implantation than the stimulated one.
Success Rates: Fresh vs Frozen
Overall Success Rates by Age
| Age Group | Fresh Transfer | Frozen Transfer (FET) |
|---|---|---|
| Under 30 | 40-45% | 45-50% |
| 30-34 | 35-40% | 40-48% |
| 35-37 | 28-33% | 35-42% |
| 38-40 | 18-25% | 22-30% |
| Over 40 | 8-12% | 10-15% |
Key finding: FET has 5-10 percentage point advantage in success rates for most age groups. The benefit is most pronounced for women under 38.
Success Rates by Patient Type
PCOS Patients
Fresh Transfer: 25-30% (high OHSS risk)
FET: 45-52% (after recovery)
Dramatic improvement with freeze-all for PCOS due to OHSS avoidance
High Responders (>20 eggs retrieved)
Fresh Transfer: 30-35%
FET: 42-50%
High oestrogen impairs receptivity—FET allows recovery
Normal Responders (8-15 eggs, normal hormones)
Fresh Transfer: 35-42%
FET: 38-45%
Similar success—either approach works well
Poor Responders (≤5 eggs retrieved)
Fresh Transfer: 18-25%
FET: 20-28%
Marginal difference—choice depends on other factors
Why FET Often Works Better: The Science
1. Ovarian Stimulation Impairs Uterine Receptivity
During IVF stimulation, oestrogen levels reach 2,000-5,000 pg/mL (normal is 50-250 pg/mL). This supraphysiologic oestrogen causes the endometrium to "advance" faster than the embryo develops, creating asynchrony between embryo stage and uterine receptivity window.
The window of implantation is only 24-48 hours. If your uterine lining is "Day 7" when your embryo is "Day 5," they're out of sync and implantation fails. FET allows precise timing synchronisation.
2. Progesterone Elevation Before Trigger
In 10-30% of IVF cycles, progesterone rises >1.0-1.5 ng/mL before the trigger shot. This "premature progesterone elevation" reduces fresh transfer success rates by 20-30% because the lining is already progressed. FET bypasses this issue entirely since you start fresh in a new cycle.
3. Gene Expression Changes
Studies using endometrial receptivity arrays (ERA) show that stimulation medications alter expression of genes involved in implantation. These changes normalise by the next cycle, making FET uterus more "receptive" than fresh transfer uterus for many women.
4. Physical Recovery
After egg retrieval, your ovaries are enlarged (tennis ball size) and your abdomen may have fluid from follicle punctures. By waiting 4-8 weeks for FET, you're physically recovered, less bloated, and in better condition for pregnancy.
5. Embryo Selection Benefit
With freeze-all, embryologists have more time to observe embryo development to Day 6 if needed, allowing better selection. Some embryos that look "slow" on Day 5 catch up by Day 6 and become excellent blastocysts. Fresh transfer requires choosing on Day 5.
Free FET Preparation Checklist
Step-by-step guide to preparing your body for frozen embryo transfer. Includes timeline, medications, lining-building tips, and what to expect.
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Who Should Do Freeze-All?
✓ Freeze-All Strongly Recommended
- 1.PCOS patients
High OHSS risk. FET dramatically improves success and safety. - 2.High OHSS risk (>20 follicles, oestrogen >2,500 pg/mL)
Fresh transfer pregnancy hormones worsen OHSS. Freeze-all is safer. - 3.Progesterone elevation >1.5 ng/mL before trigger
Reduces fresh transfer success by 20-30%. FET bypasses this. - 4.Doing PGT-A genetic testing
Results take 7-14 days. Freeze-all mandatory. - 5.Thin endometrial lining (<7mm) or uterine issues found
Need time to improve lining or treat issues before transfer. - 6.Feeling very unwell after retrieval
Severe bloating, pain, or early OHSS symptoms. Your body needs recovery.
? Freeze-All Optional (Discuss with RE)
- •High responders (>20 eggs but normal hormones): May benefit from FET even without OHSS symptoms
- •Previous failed fresh transfer: Consider freeze-all next time to see if FET works better
- •Clinic has blanket freeze-all policy: Based on their data showing better outcomes
- •You want to maximise success: FET generally has 5-10% higher success rate
Fresh Transfer Reasonable Choice IF:
- •Normal response (8-15 eggs), normal hormone levels (oestrogen <2,500 pg/mL, progesterone <1.5 ng/mL)
- •Good lining (≥8mm, trilaminar pattern), no uterine issues
- •You want to avoid 4-8 week delay
- •Budget-conscious (save £1,500-2,500 FET cost)
- •Feeling physically well after retrieval
Cost Comparison
| Component | Fresh Transfer | Frozen Transfer (FET) |
|---|---|---|
| Standard IVF Cycle | £8,000-12,000 | £8,000-12,000 |
| Embryo Freezing | — | £500-800 (one-time) |
| Embryo Storage | — | £200-350/year |
| Transfer Procedure | Included in IVF | £1,500-2,500 |
| FET Medications | — | £200-500 |
| Total First Transfer | £8,000-12,000 | £10,400-16,150 |
| Additional Cost vs Fresh | — | £2,400-4,150 |
Value Calculation: If FET has 5-10% higher success rate, the extra £2,400-4,150 may be worth it to avoid another full IVF cycle (£8,000-12,000). However, if you have limited budget and good prognosis, fresh transfer saves money upfront.
Timeline Comparison
Fresh Transfer Timeline
Day 1: Start stimulation
Begin FSH injections
Day 10-14: Egg retrieval
Sperm fertilises eggs
Day 13-19: Embryo transfer
Day 3 or Day 5 transfer
Day 27-33: Pregnancy test
Blood hCG test
Total: 4-5 weeks from start to pregnancy test
Frozen Transfer Timeline
Day 1: Start stimulation
Begin FSH injections
Day 10-14: Egg retrieval
Fertilise and freeze all embryos
Week 4-8: Recovery period
Wait 1-2 menstrual cycles
Week 8-10: FET preparation
Lining prep, monitor cycle
Week 10: FET transfer
Thaw and transfer embryo
Week 12: Pregnancy test
Blood hCG test
Total: 10-12 weeks from start to pregnancy test
Timeline Trade-off: Fresh transfer is 6-8 weeks faster to pregnancy test. For women with time pressure (age 40+, medical urgency), this matters. But if success rate is 5-10% higher with FET, the extra wait may be worth better odds.
Pros & Cons Summary
Fresh Transfer
Pros
- • No freezing costs (£500-800 saved)
- • 6-8 weeks faster timeline
- • Continuous cycle (no interruption)
- • Good success if normal responder
- • Still have frozen embryos for later
Cons
- • 5-10% lower success vs FET (average)
- • OHSS risk if high responder
- • Uterine receptivity may be impaired
- • Can't do PGT-A
- • No time to treat uterine issues
- • Progesterone elevation risk
Frozen Transfer (FET)
Pros
- • 5-10% higher success (average)
- • Better uterine receptivity
- • Avoids OHSS risk
- • Time to optimise lining/treat issues
- • Can do PGT-A
- • 95-99% embryo survival rate
- • Physically recovered for transfer
Cons
- • Extra £2,400-4,150 cost
- • 6-8 weeks longer timeline
- • Small risk embryos don't survive thaw
- • Additional monitoring/appointments
- • More medications for lining prep
- • Emotional burden of waiting
How to Choose: Decision Guide
Choose Freeze-All (FET) IF:
- ✓You have PCOS or high OHSS risk
- ✓Oestrogen >2,500 pg/mL or >20 follicles
- ✓Progesterone >1.5 ng/mL before trigger
- ✓You're doing PGT-A testing
- ✓Your lining is thin (<7mm) or you have uterine issues
- ✓You feel very unwell after retrieval
- ✓You had previous failed fresh transfer
- ✓Maximising success is top priority (worth extra cost/time)
Choose Fresh Transfer IF:
- ✓Normal response (8-15 eggs), normal hormones
- ✓Progesterone <1.5 ng/mL, oestrogen <2,500 pg/mL
- ✓Good lining (≥8mm, trilaminar)
- ✓Feeling well after retrieval (minimal bloating/pain)
- ✓Time is critical (age 40+, medical urgency)
- ✓Budget is tight (save £2,400-4,150)
- ✓You emotionally need to keep going (can't bear waiting)
- ✓Your doctor recommends it based on your specific situation
Bottom Line: For PCOS, high responders, and those doing PGT-A, freeze-all is clearly superior. For normal responders with good hormones, either approach works—choice depends on priorities (time vs success rates vs cost). Always discuss with your RE, who can assess your specific hormone levels, lining quality, and individual factors to recommend best approach.