IVF Due Date Calculator
Calculate your IVF pregnancy due date from embryo transfer date, using ACOG's rule for pregnancies from assisted reproduction: the embryo's age and the transfer date, not the last period. Works for fresh, frozen (FET), 3-day, 5-day, and 6-day transfers.
Reviewed & updated for 2026 by Rakesh Choudhary, PhDMethodology & sources · How we calculate
Why IVF dates don't use the LMP
Standard pregnancy due dates use Naegele's rule: add 280 days to the first day of the last menstrual period (LMP), assuming a 28-day cycle with ovulation on day 14. Real cycles vary in length and ovulation doesn't always fall on day 14, which can shift the true due date.
IVF removes that assumption. The egg retrieval and embryo creation happen on a known date, in a lab. The transfer date is documented. The embryo's developmental age (3-day, 5-day, 6-day) is known. ACOG's Committee Opinion 700 therefore dates the pregnancy from the embryo's age and the transfer date: due date = transfer date + (266 days − embryo age). For a 5-day blastocyst transfer on January 15, 2026, due date = January 15 + 261 days = October 3, 2026.
The pregnancy "weeks" still get counted from the LMP equivalent (2 weeks before egg retrieval), because prenatal milestones, growth charts and screening timing are all set in weeks since the LMP. So a woman on the day of a 5-day transfer is already "2 weeks 5 days pregnant", even though the actual transfer just happened. This can feel strange but it's how the medical reference materials are calibrated.
Embryo development timeline at transfer
Day 3 transfer (cleavage stage): The embryo is a small cluster of cells. Due date = transfer + 263 days (ACOG). Clinics choose a day 3 transfer in some cases, for example when there are few embryos to choose from, or for specific patient factors.
Day 5 transfer (blastocyst): The embryo has developed into a fluid-filled ball of cells differentiated into inner cell mass (becomes the baby) and trophectoderm (becomes the placenta). Due date = transfer + 261 days (ACOG). Culturing to day 5 gives the clinic more to choose between, and allows preimplantation genetic testing (PGT-A) on a few cells from the trophectoderm.
Day 6 or 7 transfer (delayed blastocyst): Some embryos develop slower and reach blastocyst stage on day 6. The same rule gives transfer + 260 days for a day 6 embryo. Day 7 transfers are unusual; ask your clinic for the date they record.
Fresh vs frozen embryo transfer, what's different
In a fresh cycle, eggs are retrieved, fertilized, cultured for a few days (to day 3, 5 or 6), and the chosen embryo is transferred in the same cycle. The body is still under the influence of ovarian stimulation drugs.
In a frozen embryo transfer (FET), embryos from a prior cycle are thawed and transferred during a different cycle, often with hormone preparation rather than ovarian stimulation. FET also allows more flexible timing and genetic testing of embryos.
Due date math is the same. Transfer date + (266 − embryo age) regardless of fresh or frozen. The "2 weeks pregnant" counting also stays the same because the calculation is based on what cycle day the transfer effectively mimics, not on when the embryo was originally created.
Multiples and IVF: planning for an earlier delivery
Twins and triplets are born earlier on average. In the CDC's 2005 data, the average length of pregnancy at birth was 38.7 weeks for single babies, 35.2 weeks for twins, 31.9 weeks for triplets and 29.8 weeks for quadruplets. Plan childcare, parental leave, and nursery prep with an earlier birth in mind. Choosing twins or triplets in the calculator shows the date that average would fall on for your transfer.
Transferring a single embryo avoids a multiple pregnancy, which carries higher risks of preterm birth, cesarean delivery, high blood pressure in pregnancy, gestational diabetes and newborn complications. Ask your clinic how many embryos they recommend transferring in your case.
If twins are found at an early ultrasound, ask about a maternal-fetal medicine consultation. Twin pregnancies need more frequent monitoring, often more imaging, and specific testing for fetal growth concordance.
FAQs
How is IVF due date calculated?
ACOG's Committee Opinion 700 says to date a pregnancy from assisted reproduction by the embryo's age and the transfer date. Formula: Due date = Transfer date + (266 days − embryo age in days). For 3-day embryo: Transfer + 263 days. For 5-day embryo (blastocyst): Transfer + 261 days. For 6-day blastocyst, the same rule gives Transfer + 260 days.
Why is IVF dating different from LMP dating?
A Last Menstrual Period (LMP) calculation assumes a 28-day cycle with ovulation on day 14, but actual ovulation varies. With IVF, fertilization happens in the lab on a known date, so ACOG says to use the embryo's age and transfer date instead of the LMP.
What's the difference between fresh and frozen embryo transfer (FET)?
Fresh: embryos are transferred a few days after egg retrieval (day 3, 5 or 6). Frozen (FET): embryos are frozen and thawed before transfer in a later cycle. The due date calculation is the same, based on the transfer date and embryo age.
How many weeks pregnant am I after IVF?
Pregnancy weeks are counted from the LMP equivalent (2 weeks before egg retrieval). On the day of a 5-day transfer, you're already considered '2 weeks 5 days pregnant.' This is why IVF mothers see 'weeks pregnant' jump quickly after transfer; they were already 'pregnant' on paper before the transfer happened.
Is IVF due date the same for twins?
Yes, the due date calculation is the same. Twins are usually born earlier, though: in the CDC's 2005 data the average was 35.2 weeks for twins and 31.9 weeks for triplets, against 38.7 for single babies. Plan for a likely earlier delivery if you're carrying multiples.
What if my IVF baby comes early?
Like any pregnancy, IVF babies can come early. Preterm birth (before 37 weeks) affected about 1 in every 10 US babies in 2022 (CDC). NICHD says babies do best when they are born during weeks 39 and 40. If you have signs of early labor, call your provider straight away.