Last updated September 22, 2026 · Report an error
Calculates an estimated due date from an IVF embryo transfer date and the embryo's age at transfer (day 3 or day 5), using the standard published IVF due-date convention: a full-term pregnancy is 266 days from fertilization (conception), so due date = transfer date + (266 - embryo age in days) — that is, transfer date + 263 days for a day-3 transfer, or transfer date + 261 days for a day-5 transfer. This differs from a standard LMP-based Naegele's rule due date because it starts from a known fertilization date rather than an estimated one. Pure date arithmetic — for general reference and educational purposes only, not a medical diagnosis. Confirm your due date with your fertility clinic.
How it works
Enter your embryo transfer date and select whether it was a day 3 or day 5 (blastocyst) transfer. The tool adds the corresponding standard number of days.
- Enter embryo transfer date.
- Enter embryo age at transfer.
- Click Calculate to see your results.
Examples
Day 5 transfer on January 1
Due date = January 1 + 261 days.
Who should use it
- Estimating a due date shortly after a successful embryo transfer.
- Fertility clinic patient education materials.
Industry applications
- Fertility clinic patient communications
- IVF patient education
Advantages
- Uses a known date (transfer date) rather than an estimated one.
- Standard convention used by fertility clinics.
Limitations
- An estimate — your clinic's own dating (often confirmed by early ultrasound) is authoritative.
- Assumes a typical 266-day gestation length.
Common mistakes to avoid
- Confusing the transfer date with the retrieval/fertilization date.
- Using the LMP-based 280-day rule for an IVF pregnancy instead of the IVF-specific convention.
Best practices
- Use the exact transfer date from your fertility clinic's records for the most accurate estimate.
Tips
- Your clinic will typically confirm dating with an early ultrasound, which may adjust this initial estimate slightly.