IVF due dates: why day-3 and day-5 transfers use different calculations
For an IVF pregnancy, the transfer date is only one part of the dating calculation. You also need the embryo's age. ACOG recommends using embryo age and transfer date to assign the estimated due date for pregnancies resulting from assisted reproduction. ACOG: Methods for Estimating the Due Date
The two calculations
| Transfer type | Calendar calculation |
|---|---|
| Day-3 embryo | Transfer date plus 263 days |
| Day-5 embryo | Transfer date plus 261 days |
These are the offsets described in ACOG's dating guidance and used by DayCalc's IVF due-date calculator. The day-5 embryo is two days older at transfer, so two fewer days remain on the same estimated pregnancy timeline.
A worked example
Take the fictional transfer date 1 September 2026:
- A day-3 transfer gives an estimated due date of 22 May 2027.
- A day-5 transfer gives an estimated due date of 20 May 2027.
The two-day difference comes from embryo age. It does not tell you which transfer is more likely to succeed, and neither date predicts the actual birthday.
You can check the arithmetic another way: the standard 280-day gestational timeline includes 14 days before conception. Subtract those 14 days and the embryo's age: 280 − 14 − 3 = 263; 280 − 14 − 5 = 261.
What to enter
Use the transfer date and embryo age supplied by your fertility clinic. Select day-3 or day-5 as appropriate, then calculate. DayCalc supports those two ages; do not round a different age to fit the selector. Ask your clinic which dating applies if your records are unclear.
If your clinic has already assigned a due date, follow that date. ACOG says later changes to an established due date should be reserved for rare circumstances and handled clinically. A later scan is not a reason to keep changing the date yourself. ACOG dating guidance
Continue from your clinic's date
Use pregnancy weeks and days with the Estimated due date option to view the stage associated with the clinic's date. For other dating methods, use the general due-date calculator.
Prepared by DayCalc with AI assistance. Examples and offsets checked on 9 October 2026. The linked clinical guidance is the source for the dating method; it is not an endorsement of DayCalc. This guide has not been clinically reviewed and provides general information, not individual medical advice.