Dr. Neha Yadav — verify qualifications, designation and registration details before publication.
In Brief
Fresh and frozen embryo transfers offer approximately the same chance of having a baby over a complete IVF cycle for most women.
However, freezing all suitable embryos may be preferable when there is a higher risk of ovarian hyperstimulation syndrome (OHSS), genetic testing is planned, or progesterone levels rise early. A fresh transfer may remain reasonable when there is no specific clinical reason to delay transfer.
A frozen embryo transfer (FET) cycle generally takes around three weeks from the first day of the menstrual period to the transfer, followed by a pregnancy blood test approximately two weeks later.
You Have Embryos in the Freezer. What Happens Next?
After an IVF cycle, some couples may have embryos frozen for future use. In other situations, the fertility team may recommend freezing all suitable embryos instead of transferring one during the same stimulation cycle.
This is commonly called a freeze-all approach.
It can raise several questions:
Is a frozen embryo transfer more successful than a fresh transfer?
Why would a doctor recommend freezing all embryos?
How long does a frozen embryo transfer cycle take?
Is a natural cycle better than a medicated cycle?
Does freezing affect embryo survival?
Neither fresh nor frozen transfer is automatically the right choice for everyone. The decision depends on the woman's response to ovarian stimulation, hormone levels, uterine lining, embryo-related requirements and overall health.
For information about IVF and fertility services, visit Renew Healthcare.
What Is the Difference Between Fresh and Frozen Embryo Transfer?
Fresh Embryo Transfer
In a fresh transfer, an embryo is transferred into the uterus during the same IVF cycle in which the eggs were collected.
After ovarian stimulation and egg retrieval, the eggs are fertilised in the laboratory. If the clinical conditions are suitable, an embryo may be transferred without waiting for another menstrual cycle.
Frozen Embryo Transfer (FET)
In a frozen embryo transfer, suitable embryos are frozen using a process called vitrification. An embryo is then warmed and transferred during a later cycle.
The original stimulation cycle is completed without an embryo transfer when the clinic follows a freeze-all approach.
What Does Freeze-All Mean?
Freeze-all means that no embryo is transferred during the ovarian stimulation cycle. All suitable embryos are vitrified, and an embryo is warmed for transfer in a later cycle.
Vitrification has made embryo freezing a dependable part of modern IVF practice. Freezing may also be necessary when genetic testing is planned because the results can take days or weeks.
Another important reason is OHSS. In women who develop a high ovarian response, becoming pregnant immediately after stimulation can increase the risk of OHSS or make it more serious.
The proportion of IVF cycles involving frozen transfers has increased in several countries. For example, UK data reported that frozen transfers accounted for 48% of IVF cycles in 2024, compared with 24% in 2014. A comparable published national figure for India was not identified in the source research.
Fresh vs Frozen Embryo Transfer: What Do Studies Show?
The most important question is whether frozen embryo transfer actually increases the chance of having a baby.
The answer depends on the patient group and the outcome being measured.
A Cochrane review of eight trials involving 4,712 women found no clear overall advantage in cumulative live-birth rates for frozen transfer compared with fresh transfer. The pooled odds ratio was 1.08, with a confidence interval of 0.95 to 1.22.
This means that when outcomes from the complete IVF cycle are considered, the overall chance of a baby was broadly similar.
However, some groups may benefit from a frozen transfer.
| Patient group or situation | What research found | Interpretation |
|---|---|---|
| Women overall | Similar cumulative live-birth outcomes in the pooled trials | No clear overall advantage for either approach |
| Women with PCOS | One large trial found a higher live-birth rate after the first frozen transfer | Frozen transfer may benefit this group |
| Women who ovulate normally using day-3 embryos | Trials found no significant difference | Fresh and frozen were broadly comparable |
| Good-prognosis women receiving a single blastocyst | One trial found a higher singleton live-birth rate with frozen transfer | A possible benefit in this particular setting, with a safety trade-off |
What About Women With PCOS?
A large trial involving 1,508 women with PCOS compared fresh and frozen embryo transfers.
The first-transfer live-birth rate was:
49.3% in the frozen-transfer group.
42.0% in the fresh-transfer group.
The trial also reported lower OHSS in the frozen group, but a higher rate of pre-eclampsia.
These findings suggest that frozen transfer may be particularly useful for some women with PCOS. They should not be treated as a guarantee or applied to every IVF patient.
Read more about PCOS and fertility treatment.
Does Frozen Transfer Always Improve Success?
No.
A trial involving good-prognosis women receiving a single blastocyst reported a higher singleton live-birth rate with frozen transfer. However, pre-eclampsia was also more frequent in the frozen-transfer group.
Other trials involving different patient groups did not find a significant advantage.
The UK E-Freeze trial also found no evidence supporting routine freeze-all for everyone. The authors advised using it when there is a definite clinical indication.
The key point: Freeze-all is a useful clinical strategy in selected situations, not a method that automatically makes IVF more successful for every woman.
When Is Freeze-All Recommended?
Freezing all suitable embryos may be considered when there is a specific reason to avoid fresh transfer.
1. Higher Risk of Ovarian Hyperstimulation Syndrome
Women who develop a large number of follicles or have a high ovarian response may be at increased risk of OHSS.
A pregnancy during the same cycle can worsen OHSS because pregnancy-related hormones may prolong or intensify the condition.
A freeze-all strategy can reduce this risk.
2. Genetic Testing Is Planned
When preimplantation genetic testing (PGT) is planned, embryos may need to be frozen while the laboratory completes the testing process.
The embryo can then be considered for transfer in a later cycle according to the clinical plan.
Important: PGT must not be used for sex selection. Sex selection is prohibited in India under the PCPNDT Act, 1994 and the ART Act, 2021.
Read more about genetic testing in IVF.
3. Progesterone Levels Rise Early
If progesterone rises earlier than expected on the trigger day, the uterine lining may not be optimally synchronised with the embryo.
Research involving more than 60,000 IVF cycles found that early progesterone elevation was associated with lower pregnancy rates after fresh transfer, but not in the same way after frozen transfer.
The relevant cut-off depends on the laboratory and its testing method.
4. The Uterine Lining Is Not Ready
A transfer may be postponed if the uterine lining is not considered suitable or if fluid is present in the uterine cavity.
A woman's general health and any other clinical concerns also matter.
When Can Fresh Transfer Be Reasonable?
Fresh transfer may be appropriate when:
The ovarian response is moderate.
OHSS risk is low.
Progesterone has remained within the clinic's acceptable range.
The uterine lining is suitable.
No PGT is planned.
There is no other clinical reason to delay transfer.
A useful question to ask your fertility specialist is:
"Which specific reason applies to me, or is freeze-all simply the routine approach?"
Frozen Embryo Transfer Cycle: Day-by-Day Guide
A frozen embryo transfer cycle can be planned in different ways.
The two broad approaches are:
Natural or modified natural cycle.
Programmed or hormone-replacement cycle.
The choice depends partly on whether the woman ovulates regularly and whether a fixed transfer date is needed.
Natural or Modified Natural FET
In a natural cycle, the woman's own ovulation determines the timing of the transfer.
In a modified natural cycle, a trigger injection may be used to help fix the timing.
Programmed FET
In a programmed cycle, medication is used to prepare the uterine lining. Oestradiol helps build the lining, followed by progesterone to prepare it for embryo transfer.
Because the cycle is hormonally prepared, the timing can be scheduled more predictably. A programmed cycle does not form a corpus luteum because ovulation does not occur in the usual way.
FET Timeline: Natural vs Programmed Cycle
| Cycle stage | Natural or modified natural cycle | Programmed cycle |
|---|---|---|
| Days 1–4 | Period begins; baseline scan if required | Period begins; oestradiol may start around day 2–4 |
| Days 10–14 | Repeated scans and blood tests to monitor ovulation or trigger timing | A scan may be performed around day 12–14 to assess the lining |
| After lining or ovulation assessment | Transfer date is planned according to ovulation or trigger | Progesterone begins when the lining is considered ready |
| Embryo transfer | Around five days after ovulation for a day-5 embryo, or three days for a day-3 embryo | A blastocyst is generally transferred after about five days of progesterone |
| After transfer | Pregnancy blood test is usually planned about two weeks later | Pregnancy blood test is usually planned about two weeks later |
The complete cycle generally takes around three weeks from the first day of the menstrual period to transfer. The exact schedule varies according to the patient's response and the clinic's protocol.
In a programmed cycle, hormone support may continue into early pregnancy according to the treating clinic's protocol.
How Many Clinic Visits Are Needed?
The number of monitoring visits can differ between protocols.
One trial reported an average of:
3.0 monitoring visits in natural cycles.
2.4 monitoring visits in programmed cycles.
These figures come from one study and should not be treated as a fixed schedule for every clinic or patient.
Natural vs Programmed FET: Which Is Better?
Both approaches can result in a successful pregnancy. The main difference is how the uterine lining is prepared and how the transfer date is determined.
Natural Cycle FET
A natural cycle uses the woman's own ovulation to determine transfer timing.
Potential considerations include:
It follows the body's natural hormonal cycle.
It forms a corpus luteum after ovulation.
It may require repeated scans and blood tests to monitor ovulation.
Timing can be less predictable if ovulation is irregular.
Programmed FET
A programmed cycle uses hormones to prepare the uterine lining.
Potential considerations include:
Transfer timing can be planned more predictably.
It may be useful for women who do not ovulate regularly.
It may be appropriate in premature ovarian insufficiency.
It does not form a corpus luteum.
Why Does the Corpus Luteum Matter?
The corpus luteum forms after ovulation. It produces hormones that help the mother's blood vessels adapt during early pregnancy.
A programmed FET cycle does not form a corpus luteum because it does not rely on natural ovulation.
Some observational studies have reported higher rates of hypertensive disorders, including pre-eclampsia, after programmed frozen embryo transfer compared with natural-cycle transfer.
One cohort reported pre-eclampsia in 12.8% of programmed-cycle pregnancies compared with 3.9% after modified natural cycles. A separate meta-analysis also found an association between programmed cycles and hypertensive disorders.
However, these findings do not prove that the absence of a corpus luteum directly causes the difference. Randomised trials have not fully established the safety differences.
For women who ovulate regularly, it is reasonable to ask whether a natural or modified natural FET is suitable. A programmed cycle may still be appropriate when there is a clinical reason, such as irregular or absent ovulation or the need for fixed timing.
Do All Frozen Embryos Survive Thawing?
No. Not every embryo survives warming.
Vitrification is a rapid freezing method that has improved embryo survival compared with older slow-freezing techniques.
A systematic review found better embryo survival after vitrification than slow freezing, with a relative risk of 1.59 across seven trials involving 3,615 embryos.
However, this does not mean every embryo will survive the warming process.
It is useful to ask the embryology laboratory:
What is the laboratory's own embryo thaw-survival rate?
What happens if an embryo does not survive warming?
Is another embryo warmed on the same day if needed?
Are there additional charges for warming another embryo?
The answers can help couples understand the laboratory process and any additional costs.
Why Is Single Embryo Transfer Important?
Transferring more embryos does not automatically mean a better overall outcome.
Evidence reviewed in the source material suggests that repeated single-embryo transfers may achieve a similar cumulative live-birth outcome to a double-embryo transfer, while reducing multiple pregnancies.
Frozen embryo storage makes it possible to transfer another suitable embryo in a later cycle if needed.
The number of embryos to transfer should be decided with the treating specialist, taking embryo quality, age, medical history and applicable clinical guidance into account.
Read more about why transferring one embryo can be safer.
What Does a Frozen Embryo Transfer Add to the Cost?
A frozen embryo transfer may involve additional charges beyond the original ovarian stimulation cycle.
The cost may include:
Embryo vitrification.
Embryo storage, often charged annually.
Embryo warming.
Medicines used to prepare the uterine lining.
Ultrasound scans and blood tests.
The embryo transfer procedure.
Hormonal support after transfer.
Ask the clinic for an itemised estimate so you can understand which services are included and which may be billed separately.
Frequently Asked Questions
1. Is a frozen embryo transfer more successful than a fresh one?
Not for every woman. Across complete IVF cycles, research has found broadly similar cumulative live-birth outcomes. Some groups, including women with PCOS, may have better first-transfer outcomes with frozen transfer. The decision should depend on the clinical indication rather than a general assumption that frozen is always better.
2. Natural cycle or medicated FET: which is better?
Live-birth outcomes have been broadly similar in the available trial evidence. Natural or modified natural cycles retain the corpus luteum, while programmed cycles do not. Observational studies have associated programmed cycles with more hypertensive disorders, although this does not prove causation. The most appropriate protocol depends on ovulation and individual clinical circumstances.
3. How long does a frozen embryo transfer cycle take?
A typical FET cycle takes approximately three weeks from the first day of the period to embryo transfer. The blood pregnancy test is generally performed about two weeks later. The actual timing depends on the cycle type and individual response.
4. Do I have to wait a month after egg collection before a frozen transfer?
Not necessarily. A systematic review of 15 cohort studies found no lower live-birth outcome when frozen transfer took place in the immediate next cycle, although the evidence was of low quality. Cysts, irregular ovulation or other clinical factors may require a delay.
5. Do all embryos survive thawing?
No. Vitrification improves survival compared with older slow-freezing methods, but some embryos may not survive warming. Ask the laboratory about its own thaw-survival data and what happens if another embryo needs to be warmed.
6. Why are frozen transfers associated with more pre-eclampsia and larger babies in some studies?
Some trials and observational studies have reported higher odds of hypertensive disorders and large-for-gestational-age babies after freeze-all. The reason is not fully established. One proposed explanation for the blood-pressure findings relates to the absence of a corpus luteum in programmed cycles, but this has not been proven to explain all the observed differences.
The Bottom Line
Fresh and frozen embryo transfers offer broadly similar chances of having a baby over a complete IVF cycle for most women.
Freeze-all may be the more appropriate option when OHSS risk is high, PGT is planned, progesterone rises early or the uterine lining is not ready. Fresh transfer can remain reasonable when these clinical concerns are absent.
A frozen embryo transfer usually takes around three weeks to reach transfer, followed by a pregnancy blood test approximately two weeks later. Natural, modified natural and programmed cycles each have different considerations.
The best approach is an individualised plan based on your ovarian response, hormone levels, uterine lining, ovulation pattern and medical history.
For information about IVF and fertility services, visit Renew Healthcare. You can also read the Dr. Neha Yadav profile.
About the Doctor
Dr. Neha Yadav
Read more about Dr. Neha Yadav at Renew Healthcare.
For information about the clinic and its services, visit Renew Healthcare.
Medical Disclaimer
This article is intended for general educational purposes and does not replace individual medical advice, diagnosis or treatment. Fresh or frozen embryo transfer decisions depend on personal medical history, ovarian response, hormone levels, embryo-related factors and the treating specialist's assessment. Please consult a qualified fertility specialist for advice about your situation.
AI disclosure: This article was drafted with AI assistance and must be reviewed, edited and approved by the named medical reviewer before publication. Add the doctor's verified qualifications and NMR/SMR registration details before publishing.
References
Zaat T, Zagers M, Mol F, Goddijn M, van Wely M, Mastenbroek S. Fresh versus frozen embryo transfers in assisted reproduction. Cochrane Database of Systematic Reviews. 2021;2. doi:10.1002/14651858.CD011184.pub3.
Chen ZJ, Shi Y, Sun Y, et al. Fresh versus frozen embryos for infertility in the polycystic ovary syndrome. New England Journal of Medicine. 2016;375(6):523–533. doi:10.1056/NEJMoa1513873.
Shi Y, Sun Y, Hao C, et al. Transfer of fresh versus frozen embryos in ovulatory women. New England Journal of Medicine. 2018;378(2):126–136. doi:10.1056/NEJMoa1705334.
Vuong LN, Dang VQ, Ho TM, et al. IVF transfer of fresh or frozen embryos in women without polycystic ovaries. New England Journal of Medicine. 2018;378(2):137–147. doi:10.1056/NEJMoa1703768.
Wei D, Liu JY, Sun Y, et al. Frozen versus fresh single blastocyst transfer in ovulatory women: a multicentre, randomised controlled trial. The Lancet. 2019;393(10178):1310–1318. doi:10.1016/S0140-6736(18)32843-5.
Maheshwari A, Bell JL, Bhide P, et al. Elective freezing of embryos versus fresh embryo transfer in IVF: a multicentre randomized controlled trial in the UK (E-Freeze). Human Reproduction. 2022;37(3):476–487. doi:10.1093/humrep/deab279.
ESHRE Guideline Group on Ovarian Stimulation. ESHRE guideline: ovarian stimulation for IVF/ICSI: an update in 2025. Human Reproduction. 2026;41(4):498–514. doi:10.1093/humrep/deag018.
Human Fertilisation and Embryology Authority. Fertility Treatment 2024: Trends and Figures. June 2026.
Human Fertilisation and Embryology Authority. Treatment Add-ons: Elective Freeze All Cycles. Published 16 October 2023.
Venetis CA, Kolibianakis EM, Bosdou JK, Tarlatzis BC. Progesterone elevation and probability of pregnancy after IVF: a systematic review and meta-analysis of over 60,000 cycles. Human Reproduction Update. 2013;19(5):433–457. doi:10.1093/humupd/dmt014.
Ho VNA, Pham TD, Nguyen NT, et al. Livebirth rate after one frozen embryo transfer in ovulatory women starting with natural, modified natural, or artificial endometrial preparation in Viet Nam: an open-label randomised controlled trial. The Lancet. 2024;404(10449):266–275. doi:10.1016/S0140-6736(24)00756-6.
Geysenbergh B, Debrock S, Lie Fong S, et al. Natural versus artificial cycle for endometrial preparation in ovulatory women undergoing frozen-thawed embryo transfer: a randomised controlled trial. Human Reproduction. 2026;41(8):1420–1429. doi:10.1093/humrep/deag095.
Ghobara T, Gelbaya TA, Ayeleke RO. Cycle regimens for endometrial preparation prior to frozen embryo transfer. Cochrane Database of Systematic Reviews. 2025;6. doi:10.1002/14651858.CD003414.pub4.
von Versen-Höynck F, Schaub AM, Chi YY, et al. Increased preeclampsia risk and reduced aortic compliance with in vitro fertilization cycles in the absence of a corpus luteum. Hypertension. 2019;73(3):640–649. doi:10.1161/HYPERTENSIONAHA.118.12043.
Busnelli A, Schirripa I, Fedele F, Bulfoni A, Levi-Setti PE. Obstetric and perinatal outcomes following programmed compared to natural frozen-thawed embryo transfer cycles: a systematic review and meta-analysis. Human Reproduction. 2022;37(7):1619–1641. doi:10.1093/humrep/deac073.
Roelens C, Santos-Ribeiro S, Mackens S, et al. The impact of endometrial preparation on pregnancy loss in vitrified-warmed euploid blastocyst transfer cycles: a randomized controlled trial. Human Reproduction. 2026;41(6):910–917. doi:10.1093/humrep/deag060.
Rienzi L, Gracia C, Maggiulli R, et al. Oocyte, embryo and blastocyst cryopreservation in ART: systematic review and meta-analysis comparing slow-freezing versus vitrification. Human Reproduction Update. 2017;23(2):139–155. doi:10.1093/humupd/dmw038.
Kamath MS, Mascarenhas M, Kirubakaran R, Bhattacharya S. Number of embryos for transfer following in vitro fertilisation or intra-cytoplasmic sperm injection. Cochrane Database of Systematic Reviews. 2020;8. doi:10.1002/14651858.CD003416.pub5.
Bergenheim SJ, Saupstad M, Pistoljevic N, et al. Immediate versus postponed frozen embryo transfer after IVF/ICSI: a systematic review and meta-analysis. Human Reproduction Update. 2021;27(4):623–642. doi:10.1093/humupd/dmab002.