Frozen–thawed embryo transfer (FET) calculator
Generates an approximate schedule for a frozen embryo transfer of a Day-5 blastocyst. The medicated pathway can start either from the downregulation cycle (Norethisterone-programmed, as in the stimulation cycle dates calculator) or directly from the treatment-cycle first day of bleed. The modified-natural pathway works from the first day of the period in the treatment cycle. Exact dates follow your clinic’s protocol.
Inputs
Schedule
| Step | Date | Notes |
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Methods
In the medicated pathway, Norethisterone is taken from day 14 to day 25 of the downregulation cycle (as in the stimulation cycle dates calculator). A few days after stopping it, a withdrawal bleed marks day 1 of the treatment cycle. Oestradiol is started on day 3 of the bleed to build the lining, which is scanned at about cycle day 10 (~7 days of oestrogen); progesterone begins on cycle day 14, and a Day-5 blastocyst is transferred on the 6th day of progesterone (progesterone start + 5 days). A viability scan is booked at 6 weeks 3 days of gestation. In the modified-natural pathway the cycle is tracked from the first day of the period; an hCG trigger is given (estimated from cycle length, or entered), the day after the trigger is day 0 and progesterone is started, and a Day-5 blastocyst is transferred 5 days later (day 0 + 5). The estimated due date is the transfer date + (266 − embryo day) days. Intervals are idealised and vary between clinics and patients.