How to use it
- Choose Start from: the embryo transfer date or the egg retrieval date.
- Enter that date and, for a transfer, the Embryo age at transfer in days.
- Read the Estimated due date, the Gestational age today and the IVF timeline.
How the due date is worked out
After IVF, the clinic counts pregnancy from egg retrieval, or from co-incubation, the day the eggs and sperm are combined, and sets the start used for dating 14 days before that day (Wikipedia, Estimated date of delivery). A pregnancy counted from that start lasts 280 days, so the due date is the fertilisation day plus 266 days. Tunon and colleagues (2000) compared this start with ultrasound measurements in pregnancies after IVF.
From an embryo transfer, the fertilisation day is the transfer day minus the embryo's age. A 3-day embryo therefore adds 263 days to the transfer date, and a 5-day embryo adds 261 days. Cleavage-stage embryos are transferred on days 2 to 4 and blastocysts on days 5 or 6 after co-incubation (Wikipedia, Embryo transfer).
These dates are estimates and not medical advice. ACOG (2017) says the due date should be set as soon as the last-period data or the first accurate ultrasound is available, so ask your clinic to confirm it.
From egg retrieval: due date = retrieval day + 266 days
From a transfer: due date = transfer day + 266 days - embryo age
3-day embryo: transfer day + 263 days
5-day embryo: transfer day + 261 days
Gestational age: today - (fertilisation day - 14 days)The IVF timeline
The timeline lists the fertilisation day, the transfer day (for a transfer) and the due date. Gestational age on each row is counted the same way as for a last period, so the fertilisation day is 2 weeks 0 days and the due date is 40 weeks 0 days. For the weeks, the trimesters and the milestones of each week, see the pregnancy calendar.
What this calculator does not include
- An early ultrasound, which can change the due date after the dates you entered.
- A clinic that counts from a different day. Use the dates in your treatment records if they differ from the ones you enter.
- Advice on treatment or symptoms. Ask your clinic or doctor about anything that worries you.
Worked example: embryo transfer on September 1, 2026, 5-day embryo
Fertilisation day: September 1, 2026 minus 5 days = August 27, 2026.
Due date: September 1, 2026 + 266 - 5 = September 1, 2026 + 261 days = May 20, 2027.
On November 10, 2026 the count started on August 13, so the pregnancy is 89 days old: 12 weeks 5 days, with 191 days left until the due date.
| Date | Event | Gestational age |
|---|---|---|
| August 27, 2026 | Fertilisation (embryo day 0) | 2 weeks 0 days |
| September 1, 2026 | Embryo transfer, embryo day 5 | 2 weeks 5 days |
| May 20, 2027 | Estimated due date (40+0) | 40 weeks 0 days |
Frequently asked questions
Is the due date after IVF counted differently from a natural pregnancy?
The term is the same 280 days, but the count starts from fertilisation rather than from the last period. After IVF the fertilisation day is known, so the due date can be counted from it (Wikipedia, Estimated date of delivery).
Why does a 5-day embryo give an earlier due date than a 3-day embryo transferred on the same day?
The 5-day embryo was fertilised two days before a 3-day embryo would have been on that transfer day, so it is two days further along. Its due date is therefore two days earlier than the 3-day one.
Does the egg retrieval date or the transfer date give the better estimate?
The retrieval date gives the fertilisation day directly when the eggs and sperm are combined that day. The transfer date needs the embryo's age, which the clinic records. If your clinic's dates differ from these, use theirs.
Why is the gestational age 2 weeks at fertilisation?
Pregnancy is counted from 14 days before fertilisation, the same origin as a last period. So on the fertilisation day the count is 2 weeks 0 days (Wikipedia, Estimated date of delivery).
Does this calculator store the dates I enter?
No. The calculation runs in your browser and nothing you enter is sent to us.
Sources
- Tunon K et al. (2000): Gestational age in pregnancies conceived after in vitro fertilization, Ultrasound Obstet Gynecol 15:41-46 (PubMed)
- ACOG Committee Opinion 700: Methods for Estimating the Due Date (2017, PubMed)
- Estimated date of delivery, the IVF origin of gestational age (Wikipedia)
- Embryo transfer, cleavage and blastocyst stages (Wikipedia)
Figures and text last checked on Tuesday, November 10, 2026.