Embryo Freezing & Frozen Embryo Transfer (FET) in Kolkata | Abha Surgy Centre

What is embryo freezing?

Embryo freezing — formally called embryo cryopreservation — is the practice of preserving surplus embryos from an IVF cycle for future use. After eggs are fertilised in the lab and grown to the blastocyst stage (Day 5–6), the strongest embryo is usually transferred fresh, while remaining high-quality embryos are vitrified.

Vitrification is an ultra-fast freezing technique that takes embryos from body temperature to –196 °C in a fraction of a second, preventing the formation of ice crystals that used to damage embryos in the older "slow-freeze" era. Post-thaw survival with modern vitrification is typically 95%+, and surviving embryos behave almost identically to fresh embryos in subsequent transfers.

Frozen embryos can be stored safely for many years. When you are ready, they are thawed and transferred in a frozen embryo transfer (FET) cycle — a much simpler, gentler, and cheaper procedure than a fresh IVF cycle.

Why embryo freezing matters

In modern IVF, embryo freezing is no longer a backup plan — it is often the primary strategy. There are several reasons:

1. Cumulative success per egg retrieval

A single egg retrieval often produces several good embryos. By freezing extras, one stimulation cycle can support multiple transfer attempts and, eventually, multiple pregnancies (siblings).

2. "Freeze-all" cycles for safety

In some cases — particularly PCOS patients at risk of ovarian hyperstimulation, or patients with thin endometrium during stimulation — we deliberately freeze every embryo and transfer in a later, calmer cycle. Outcomes are better and risks lower.

3. Better uterine receptivity

Recent evidence suggests that the high hormone levels of a stimulation cycle can make the uterine lining slightly less receptive in some women. A FET cycle uses gentler preparation (natural cycle or hormone-supported), often improving implantation in PCOS, recurrent failure, and over-35 cases.

4. PGT-A genetic testing

If you are screening embryos with PGT-A for chromosomal status, results take 1–2 weeks. Embryos must be vitrified during the wait. Transfer happens in a subsequent FET cycle.

5. Family completion later

Frozen embryos let you return for a second baby years later without repeating stimulation, retrieval, or fertilisation. Many of our families have a second child via FET 2–4 years after their first.

When embryo freezing is recommended

Beyond storing surplus embryos, deliberate freeze-all cycles are recommended in:

• High AMH or PCOS patients at risk of ovarian hyperstimulation syndrome (OHSS).
• High progesterone on trigger day, which can compromise the fresh-cycle endometrium.
• Thin or unfavourable endometrium during stimulation.
• PGT-A genetic screening cycles.
• Patients undergoing fertility-preservation before cancer treatment, when there is a partner or donor sperm available (embryo freezing is generally more efficient than egg freezing).
• Same-sex female couples using donor sperm and planning multiple pregnancies.
• Sequential transfers — separating retrieval and transfer into two calmer events.

How embryo freezing works at Abha Surgy Centre

Embryo freezing happens entirely in our on-site embryology lab. Here is what is happening behind the scenes:

1. Embryo selection. On Day 5 or 6, embryologists assess each blastocyst's morphology and grade (e.g. 4AA, 4AB) using validated criteria. Only embryos meeting quality thresholds are selected for freezing.
2. Loading. Each embryo is placed individually on a fine cryo-storage device (Cryotop or similar) and exposed briefly to a cryoprotectant solution.
3. Vitrification. The device is plunged directly into liquid nitrogen, freezing the embryo in milliseconds.
4. Storage. Devices are placed in alarmed, 24/7-monitored liquid-nitrogen storage tanks. Each embryo is identified by triple-witness electronic tagging.
5. Annual review. We send written annual reminders to renew consent and confirm storage continuation.

When the time comes, embryos are thawed in reverse — typically with 95%+ survival — and prepared for transfer.

The FET (frozen embryo transfer) cycle

A FET cycle is far simpler than fresh IVF and lasts about 3–4 weeks. There are two main approaches:

Natural-cycle FET

Used for women with regular ovulation. We monitor your natural cycle with 2–3 ultrasounds, time embryo transfer to the optimal post-ovulation day, and add minimal progesterone support.

Hormone-prepared FET

Used for women with irregular cycles or after PGT-A. Estrogen tablets prepare the uterine lining, progesterone is started at a defined day, and embryo transfer is timed precisely. This gives full control over scheduling.

The transfer itself

Embryo transfer is identical to a fresh IVF transfer:

• Thawed embryo loaded into a soft transfer catheter.
• Catheter passed gently through the cervix under abdominal ultrasound guidance.
• Embryo placed in the optimal location in the uterine cavity.
• Procedure takes 10–15 minutes, painless, no anaesthesia.
• You walk out the same hour.

A blood beta-hCG test 10–12 days later confirms whether implantation has succeeded.

FET success rates

Modern vitrification has made FET outcomes equal to or better than fresh transfers in many patient groups. Approximate live-birth rates per FET cycle, by age:

Maternal age	Live birth / FET cycle
Under 35	55–60%
35–37	45–50%
38–40	30–38%
41+	18–22%

PGT-A-screened euploid embryos achieve 60–65% live birth per transfer, regardless of maternal age, because the chromosomal status of the transferred embryo is known.

Embryo freezing and FET cost at Abha Surgy Centre

Item	Cost (₹)
Vitrification (within IVF cycle)	included
First-year storage	included
Annual storage (Year 2 onwards)	10,000 / year
FET cycle: natural	60,000 – 70,000
FET cycle: hormone-prepared	70,000 – 85,000
Endometrial scratch (if indicated)	+ 4,000
Add-on medications (estrogen, prog.)	included

A FET cycle costs roughly 40–50% of a fresh IVF cycle, since stimulation, retrieval, and embryology lab work have already been completed.

Frequently asked questions

How long can embryos stay frozen? There is no defined upper limit on storage time. Babies have been born from embryos stored for 25+ years. Embryo quality at thaw is the same as at freeze.

Will my embryos survive the thaw? With vitrification, our survival rate is consistently 95%+ at the blastocyst stage. Triple-witness identification, alarmed tanks, and emergency-power backup minimise any storage risk.

Are FET babies as healthy as fresh-IVF babies? Yes. Multiple large studies show FET babies are as healthy as fresh-IVF and naturally conceived babies. Some studies suggest FET pregnancies have lower rates of preterm birth and low birth weight than fresh IVF.

What happens to my embryos if I no longer want them? You have three options, and we will discuss them with full counselling support:

• Continued storage for future use.
• Donation to research (with informed consent).
• Compassionate disposal under your written authorisation.

Can I move my frozen embryos to another clinic? Yes. We support transfers to any accredited fertility centre with appropriate paperwork.

Should I do a freeze-all rather than fresh transfer? That depends on your stimulation response, hormone levels on trigger day, endometrial thickness, and whether you are doing PGT-A. Your specialist will advise you on cycle day 9–11 — not in advance.

Ready to talk?

Whether you have surplus embryos in another centre, are starting a fresh IVF cycle, or are considering a FET for a second baby, book a free consultation at Gariahat or Behala. We will review your existing embryo report (if you have one) and walk you through realistic options.

Call +91 98310 95626 or book online.