After IVF, your due date is calculated from the embryo transfer date and the age of the embryo, not from your last period. For a day 5 blastocyst transfer, add 261 days to the transfer date; for a day 3 transfer, add 263 days. Because the dates are known exactly, this is the most precise way to date a pregnancy.
Why IVF dates are more precise
In a natural pregnancy, the due date is 280 days after the first day of the last period, assuming ovulation around day 14. With IVF, fertilisation happens on a known day and the embryo's age at transfer is known, so there is no need to estimate when ovulation happened.
The formula by transfer type
| Transfer | Days to add to transfer date | Pregnancy age on transfer day |
|---|---|---|
| Day 3 embryo | 263 | 2 weeks and 3 days |
| Day 5 blastocyst | 261 | 2 weeks and 5 days |
| Day 6 blastocyst | 260 | 2 weeks and 6 days |
| Egg retrieval or insemination date | 266 | 2 weeks |
The logic is simple: pregnancy is counted as if the last period started 14 days before fertilisation, so a 5-day-old embryo is "2 weeks and 5 days" on the day it is transferred. The due date is 40 weeks after that imaginary last period.
Fresh or frozen transfers
The formula is the same for fresh and frozen embryo transfers. The time an embryo spends frozen does not count, because development pauses while it is frozen. What matters is the embryo's age when it is transferred.
Does the first scan change the date?
Professional guidance recommends using the date derived from the IVF treatment for pregnancies conceived this way. Your first scans check that the pregnancy is developing as expected; if growth is very different from what the dates suggest, your healthcare team will decide how to follow it up.
Twins after IVF
The due date for twins is calculated in the same way. Twin pregnancies are more likely to be born before 37 weeks, and your care team will plan the timing of birth with you.
Calculate your due date
Enter your transfer date and embryo age in our IVF due date calculator.
To see how many months that is, use the weeks to months calculator or read our pregnancy weeks to months guide. Your clinic's dates always take priority. Bloom Private is a cycle tracker, not a pregnancy app.
Frequently Asked Questions
Add 261 days to the transfer date. For a day 3 transfer, add 263 days, and for a day 6 transfer, add 260 days.
No. The formula is the same. What matters is the age of the embryo at transfer, not how long it was frozen.
Guidance recommends using the IVF-derived date. Your care team will decide how to follow up if growth differs a lot from the dates.