IVF & frozen transfer dating
Use your embryo transfer date and embryo age for an ART-specific estimate. The result is transparent and private; your fertility clinic’s confirmed date remains the source of truth.
Your dates stay on this device. Nothing you enter here is saved or sent to Flowy.
The calculation
ACOG’s example adds 261 days to a day-5 embryo transfer and 263 days to a day-3 embryo transfer. Both are the same underlying calculation: transfer date plus 266 days minus embryo age.
On transfer day, gestational age is conventionally 2 weeks plus the embryo’s age—2 weeks 5 days for a day-5 embryo, or 2 weeks 3 days for a day-3 embryo.
Good to know
IVF dating does not use the last menstrual period. It uses the transfer date and embryo age because those treatment dates are known. A day-5 transfer is already five days after estimated fertilization; a day-3 transfer is three days after.
This calculator supports day-3 and day-5 transfers only. If your clinic used another protocol, donor-egg timing, or gave you a different due date, use the clinic’s documented dating for care.
Common questions
ACOG gives an estimated due date 261 days after a day-5 embryo transfer. This is equivalent to estimating fertilization five days before transfer, then adding 266 days.
For a day-3 embryo transfer, the estimated due date is 263 days after transfer. That method accounts for the embryo already being three days old at transfer.
The date calculation uses the embryo’s age and transfer date, so the same day-3 or day-5 method can orient a frozen embryo transfer pregnancy. Follow the date provided by your fertility clinic.
Assisted reproduction provides known treatment dates, so ACOG recommends using ART-derived gestational age. A due date still estimates when birth may happen and should be confirmed by the clinical team.
