IVF due date calculator: due date from an embryo transfer

An IVF due date is more precise than one from a last period

Dating from a last period estimates when ovulation and conception occurred. After IVF both are known: the embryo's age at transfer fixes the date of fertilization. For that reason ACOG advises that the due date after IVF is assigned from the age of the embryo and the date of transfer (ACOG Committee Opinion 700, 2017, reaffirmed 2022).

A day-5 transfer gives a due date 261 days later, and a day-3 transfer 263

ACOG Committee Opinion 700 gives these two counts as its examples: the due date is 261 days from the embryo replacement date for a day-5 embryo and 263 days for a day-3 embryo. They follow from the 266 days between fertilization and birth (the 280-day convention less the 14 days from the start of the last period to ovulation), less the embryo's age at transfer. Counted the same way from the last-period convention, the pregnancy is 2 weeks and 3 days along on the day of a day-3 transfer (280 less 263 is 17 days) and 2 weeks and 5 days along on the day of a day-5 transfer (280 less 261 is 19 days). ACOG does not state these two week-and-day figures; they are our arithmetic from its counts.

Frozen embryo transfer (FET) due dates are calculated the same way

The rule ACOG gives uses two facts, the age of the embryo and the date of transfer, so a frozen embryo transfer due date is worked out in the same way as one after a fresh transfer. The calculator asks whether the transfer was fresh or frozen for context only.

The due date is the middle of a range

About 5 in 100 babies are born on their due date, and about 66 in 100 within a week of it (Khambalia and colleagues, 2013, in 18,708 single births after spontaneous labour in one Australian health district). The result gives the range around the date as well as the date itself.