A Frozen Embryo Transfer (FET) cycle takes three to four weeks from the start of the menstrual period to the pregnancy test. The cycle has six clear stages: baseline scan, lining preparation (with or without medication), monitoring scans, progesterone start, embryo thaw and transfer, and the two-week wait. The transfer itself takes 5-10 minutes and is performed without anesthesia.
A FET cycle is performed in a different month from the IVF cycle that produced the embryos. The ovaries have already done their work in a previous IVF cycle; what matters in a FET cycle is preparing the uterine lining so the thawed embryo finds a receptive home. The process is shorter and physically less demanding than a fresh IVF cycle, but precise medication timing is what makes it work.
There are three common protocol types at Cloudnine Fertility centres. The choice depends on cycle regularity, prior FET history, and whether the patient ovulates naturally.
All three protocols produce comparable success rates in regular ovulators. The choice is usually driven by practical considerations: scheduling control, medication preference, and whether the patient has irregular cycles. This article focuses primarily on the Hormone Replacement Therapy (HRT) protocol because it is the most widely used in Indian fertility centres and gives the most predictable timeline.
A decade ago, FET was a backup option for surplus embryos. Today, it is the default first transfer for many groups: women with PCOS, high responders to stimulation, anyone undergoing PGT-A (preimplantation genetic testing for aneuploidy, a test that screens embryos for chromosome number), and couples who want to avoid the risk of OHSS (ovarian hyperstimulation syndrome). Across major fertility centres in Gurgaon and Delhi NCR, the freeze-all approach - freezing all embryos from an IVF cycle and transferring later - has become the standard of care for these groups.
This page covers the procedural how-to: what happens in each stage of an FET cycle, day by day. For a comparison of FET versus fresh transfer success rates, costs, and which option suits which patient, see the FET vs fresh embryo transfer success rates in India pillar guide. That guide is the better starting point for anyone still deciding between fresh and frozen transfer. This article assumes the decision has been made to proceed with FET.
The cycle begins on day 1 of the menstrual period - the first day of full flow, not spotting. The patient calls or messages the Cloudnine Fertility centre to report this. A baseline appointment is scheduled for day 2, 3, or 4. At this appointment, a transvaginal (internal) ultrasound checks two things: that the ovaries are “quiet” (no large cysts that would interfere with the cycle) and that the endometrium (the uterine lining) is thin, as expected at the start of a cycle. Blood tests confirm hormone levels are at baseline.
If everything looks normal, the patient starts estrogen supplementation that same day in an HRT cycle. In a natural cycle, no medication is given; instead, follicle tracking begins around day 8-10. If anything is off - a cyst, an unexpectedly thick lining, abnormal hormones - the cycle may be deferred to the following month, which is far better than starting and cancelling later.
This is the longest and quietest stretch of the cycle. In an HRT cycle, daily estrogen, in tablet, vaginal tablet, or skin patch form, or sometimes a combination, helps the endometrium thicken from a baseline of 2-3 mm to the 7-8 mm threshold needed for transfer. Estrogen is usually taken at the same time each day; setting a daily phone alarm is the simplest way to stay consistent. Most patients tolerate it well; common mild side effects include breast tenderness, headaches, and bloating.
In a natural cycle, the patient is tracked rather than treated: regular ultrasounds and blood tests monitor the growing follicle and the rising estrogen levels produced by the body. In a modified natural cycle, a single hCG trigger shot is given when the follicle reaches the right size, which precisely sets the day of ovulation and therefore the day of transfer.
A scan between days 10-14 confirms that the endometrium is ready. Two features are looked for: thickness (target 7-8 mm or more) and pattern (a “trilaminar,” or three-layered, appearance, indicating the lining is responsive to estrogen). If both are satisfactory, the cycle proceeds. If the lining is thin or has an unusual pattern, the estrogen dose may be increased, the route may be changed (for example, switching from oral to vaginal estrogen, or adding skin patches), or the cycle may be paused for a few more days of build-up.
A small number of cycles - less than 5% at well-monitored Indian centers - are cancelled at this stage because the lining does not respond adequately. This is frustrating but not a treatment failure; the embryos remain frozen and a new cycle can begin the following month, often with an adjusted protocol.
Once the lining is ready, daily progesterone supplementation begins. This is the crucial timing point in the whole cycle, because the day progesterone starts is the day used to count the transfer date. Progesterone may be given as vaginal pessaries (small tablets inserted into the vagina), oil-based intramuscular injections, oral tablets, or a combination. The vaginal and intramuscular routes are most common; the choice is usually a balance of efficacy and tolerability.
Side effects during this stretch are usually mild: some breast tenderness, mild fatigue, occasional bloating, and sometimes a feeling of pelvic heaviness. These often overlap with early pregnancy symptoms, which makes the two-week wait psychologically harder - it is hard to read the body when both pregnancy and progesterone produce similar sensations.
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Transfer day is timed precisely from the start of progesterone. For a blastocyst (a 5-day-old embryo), transfer happens on the sixth day of progesterone. For a cleavage-stage day-3 embryo, transfer happens on the fourth day. Most modern FETs use blastocysts because they have a higher chance of implantation and allow better embryo selection.
In the embryology lab on the morning of transfer, the embryologist removes the vitrification straw (the thin tube holding the frozen embryo) from the liquid nitrogen storage tank and warms it through a precise temperature-controlled thawing protocol. Post-thaw survival at well-equipped Indian labs exceeds 95% due to modern vitrification techniques (an ultra-rapid freezing method that turns the cell's water into a glass-like solid without forming ice crystals). The embryo is then cultured for a short period in a temperature-controlled incubator to confirm survival and re-expansion before transfer.
The transfer itself is described in detail in Block 8.
The patient continues estrogen and progesterone throughout this window. Normal light activity resumes the same day as transfer; strict bed rest is not required and does not improve outcomes. Implantation - the embryo embedding into the uterine lining - begins 1-2 days after the transfer of a blastocyst and completes around days 5-9 post-transfer. By day 6-7 after transfer, the embryo starts producing β-hCG (beta-hCG, the pregnancy hormone), which becomes detectable in blood by day 10-14.
Most centres in Gurgaon and Delhi NCR schedule the blood pregnancy test 10-14 days after transfer. Home urine pregnancy tests are not encouraged before this point - they can give false negatives (because hCG is not yet high enough) or false positives (because residual hCG from an earlier trigger shot may still be in the system). If the blood test is positive, hormone support continues until 8-12 weeks of pregnancy, when the placenta takes over hormonal production.
The day-by-day timeline below uses the HRT protocol because it is the most widely used and gives the most predictable schedule. Natural and modified natural cycles follow a similar structure but with monitoring timing tied to natural ovulation
Three factors meaningfully shift how a FET cycle goes. They are listed not as success-rate determinants (those belong to the pillar guide) but as practical points within a cycle:
• Medication consistency. Most cycle-day adjustments and almost all preventable failures relate to medication timing rather than dose. Estrogen, progesterone, and any trigger medication must be taken at consistent times each day. A daily phone alarm and a written medication chart are simple but effective tools
• Endometrial response. Some patients build a 9 mm lining easily; others struggle to reach 7 mm. If a previous FET cycle had a thin lining, the protocol may be adjusted with higher estrogen, a different route, or the addition of agents that improve uterine blood flow
• Catheter ease at transfer. A smooth, atraumatic transfer is associated with better outcomes. If a previous transfer was difficult (because of a sharp cervical angle, for example), a “mock transfer” - a practice run with an empty catheter - is often done in a prior cycle to map the route
• Hydration and routine. Staying well hydrated supports endometrial blood flow; routine sleep helps with the natural hormonal rhythm. These are not magic bullets, but they cost nothing and make a measurable difference to comfort during the cycle
• Stress management. Stress does not reliably predict cycle outcome - the evidence is mixed - but it predicts how the cycle feels. Counselling, peer support groups, or simple practices like daily walks reduce the psychological weight of the two-week wait significantly
• Confirm the protocol type with a Cloudnine specialist: HRT, natural, or modified natural - each has different monitoring demands
• Complete any outstanding investigations - pelvic ultrasound, sometimes a hysteroscopy (a brief outpatient procedure to inspect the uterine cavity), thyroid panel, infection screen
• Get a detailed written medication schedule and clarify the timing of every dose
• Plan the practical demands of the cycle: 2-4 monitoring scans, transfer day, and the two-week wait
• Continue folic acid; stop smoking; minimise alcohol
• If injectable progesterone is part of the protocol, ask whether vaginal progesterone is an option - it is usually equally effective and more tolerable
• Take medications at exactly the same times each day; use phone alarms
• Attend every monitoring scan without skipping; they trigger key decisions like when progesterone starts
• Stay hydrated; light walking and routine activity are fine
• Avoid heavy exercise, alcohol, and unprescribed medication once progesterone has started
• Plan transfer day so the rest of the day is unhurried - ideally a day off work
• Avoid home pregnancy tests before the scheduled blood test - they create unnecessary anxiety in either direction
Most of a FET cycle proceeds without incident, but some situations need same-day clinic contact rather than waiting for the next appointment.
Anyone in Gurgaon or Delhi NCR mid-cycle should have the Cloudnine Fertility centre’s after-hours contact number saved on their phone before the cycle starts. Book a fertility consultation if any concerns arise before starting treatment.
Transfer day is short, calm, and well-rehearsed. Below is the hour-by-hour flow most patients experience at a Cloudnine Fertility centre in Gurgaon or Delhi NCR.
The procedure itself feels similar to a Pap smear (a routine cervical screening test). No anesthesia is used. The most common report from patients afterward is that the buildup was harder than the procedure itself - transfer is over before most people realise it has started.