How is an IVF due date calculated?

Count 266 days from the transfer date, then subtract the embryo age. For a 5-day blastocyst, subtract 5 days; for a 3-day embryo, subtract 3 days; for a 6-day blastocyst, subtract 6 days.

Does a 3-day or 5-day embryo change the due date?

Yes. A 5-day embryo is already 5 days older than a 3-day embryo, so its due date is 2 days earlier than a 3-day embryo transferred on the same day.

What about a 6-day (day-6) blastocyst?

Some blastocysts are frozen or transferred on day 6 rather than day 5. Subtract 6 days instead of 5, which moves the due date one day earlier than a day-5 transfer on the same date.

Is a frozen embryo transfer (FET) dated differently from a fresh transfer?

No. For both fresh and frozen transfers, dating uses the embryo's age at transfer, not the date it was created or frozen. A day-5 blastocyst thawed and transferred two years later is dated exactly like a fresh day-5 transfer.

How many weeks pregnant am I on transfer day?

On the day of a day-5 transfer you are counted as 2 weeks and 5 days pregnant; on a day-3 transfer, 2 weeks and 3 days. Gestational age in IVF starts 14 days before egg retrieval, which is why you are already 'two weeks pregnant' before the embryo is placed.

When is my beta hCG test and first scan?

Clinics usually run the first beta hCG around 9-11 days after a day-5 transfer, and the first ultrasound at roughly 6-7 weeks of gestation, about 3 weeks after that transfer. Your clinic's own schedule always takes priority.

Is an IVF due date more accurate?

IVF dates are usually more precise because the exact transfer date is known. An early ultrasound can still refine it if the embryo grew faster or slower than expected.

Why does my clinic's due date differ by a day or two?

Some clinics date from egg retrieval instead of transfer, and some round gestational age differently. A one- or two-day difference is normal and rarely changes any part of your care.

IVF Due Date Calculator

Calculate your due date after IVF, ICSI or a frozen embryo transfer (FET). Works for day-3, day-5 and day-6 embryos, fresh or frozen.

Embryo transfer date

Embryo age at transfer

Estimated due date

Friday, May 21, 2027

Based on a 5-day embryo transfer. On transfer day you are counted as 2w 5d pregnant.

This is an estimate for information only — only about 1 in 20 babies arrive on their due date. Always confirm dates with your midwife or doctor.

Your IVF timeline, week by week

Dates below assume a day-5 transfer on Wednesday, September 2, 2026. Beta hCG and scan timings are typical ranges — your clinic's schedule takes priority.

Milestone	Gestational age	Date
Transfer day	2w 5d	Wednesday, September 2, 2026
First beta hCG (typical)	4w 1d	Saturday, September 12, 2026
First ultrasound (typical)	5w 5d	Wednesday, September 23, 2026
End of first trimester	13w 6d	Thursday, November 19, 2026
Estimated due date	40w 0d	Friday, May 21, 2027

How IVF due dates are worked out

A natural pregnancy is dated from the first day of your last period, which is roughly two weeks before conception. IVF removes that guesswork: the lab knows the exact age of the embryo on transfer day, so dating starts from a known point rather than an estimate. That is why an IVF due date is usually the most reliable date you will get before your first scan.

The formula is simply transfer date + 266 days − embryo age. A day-5 blastocyst transferred today is due 261 days from now; a day-3 embryo is due 263 days from now.

Day-3 vs day-5 vs day-6 transfers

A day-3 embryo (a cleavage-stage embryo, usually 6-8 cells) is transferred three days after egg retrieval. A day-5 embryo has reached the blastocyst stage. Some blastocysts develop a little slower and are graded and frozen or transferred on day 6 — this is common and does not by itself indicate a problem.

Because the embryo is older at transfer, a day-5 transfer produces a due date two days earlier than a day-3 transfer on the same calendar date, and a day-6 transfer is one day earlier again. That is the entire difference: the pregnancy is not shorter or longer, it simply started counting from a different point.

Fresh vs frozen embryo transfer (FET)

Dating does not change between fresh and frozen cycles. What matters is the embryo's age at the moment it was frozen, because that is the age it resumes at when it is thawed. A day-5 blastocyst frozen in one cycle and transferred eighteen months later is still dated as a day-5 transfer, using the transfer date — not the retrieval date and not the freeze date.

Worked examples

Day-5 fresh transfer on 1 March: due date is 1 March + 261 days = 17 November. On transfer day you are 2w 5d pregnant.
Day-3 transfer on 1 March: due date is 1 March + 263 days = 19 November — two days later than the day-5 example.
Day-6 FET on 1 March: due date is 1 March + 260 days = 16 November, regardless of when the embryo was frozen.

When an early scan changes the date

Most clinics keep the IVF date even if a scan measures slightly ahead or behind, because the transfer date is a hard fact and a crown-rump length measurement is not. If a scan differs substantially, your clinic may re-date the pregnancy — you can compare the two with the ultrasound due date calculator and see how many weeks each date puts you at with the how many weeks pregnant am I calculator.

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