A frozen embryo transfer cycle: what to expect, step by step

A frozen embryo transfer (FET) is usually simpler and gentler than the stimulation cycle that made the embryos. There is no egg collection and no anaesthetic — the work is preparing the lining of the uterus so it's ready when the embryo arrives.

Two ways to prepare the lining

Natural cycle. If you ovulate regularly, the clinic tracks your own cycle with scans and blood tests, identifies ovulation, and schedules the transfer a set number of days later (five days after ovulation for a day-5 blastocyst). Some clinics add progesterone support. Fewer drugs, but timing depends on your body.

Medicated (hormone-replacement) cycle. Oestrogen tablets or patches build the lining from day 2 of your period; once it is thick enough (commonly 7–8 mm or more with a "triple-line" look on scan), progesterone is started. The transfer is timed from the day progesterone begins — five full days for a blastocyst. Predictable, but more medication, and progesterone (injections, pessaries or gel) continues until at least the pregnancy test and usually to 10–12 weeks if positive.

Which one is right for you depends on your cycle, history and clinic practice; both are standard.

What happens in the lab

Your embryo stays frozen until the morning of transfer (or the day before for a day-3 embryo). The embryologist:

1. Confirms your identity and the embryo's, with a witness.
2. Warms the embryo in a few minutes.
3. Checks survival and, for a blastocyst, watches for re-expansion — the cavity re-filling — over an hour or two.
4. Reports to you and the doctor how it looks.

If a blastocyst was frozen before hatching, some labs make a tiny opening in the shell (assisted hatching) to help it emerge; whether this helps is debated and depends on the case.

Transfer day

The transfer itself is the same as fresh: a speculum, a soft catheter passed through the cervix under ultrasound, the embryo released high in the uterus, the catheter checked under the microscope to confirm it's empty. Five to ten minutes. You can get up straight away — the embryo will not fall out; it sits in a film of fluid between the walls of the uterus.

The two-week wait

Progesterone continues. There is no evidence that bed rest, particular foods, or avoiding stairs changes the outcome; normal life is fine. Light bleeding or spotting can happen either way and doesn't tell you the result. The pregnancy test — a blood test around 9–12 days after a blastocyst transfer — is the only reliable answer; home tests can be falsely reassuring or falsely negative because of the medication and timing.