How an IVF due date is worked out
An IVF due date comes from the day the egg was fertilized, because with IVF that day is known exactly. A pregnancy lasts about 266 days from fertilization. Doctors add two weeks to count from a notional last period, which is why a pregnancy is called 40 weeks long.
An embryo is already a few days old when it’s transferred, so the count starts earlier than transfer day:
| What you know | Due date |
|---|---|
| Day-5 embryo (blastocyst) transfer | Transfer date + 261 days |
| Day-6 embryo transfer | Transfer date + 260 days |
| Day-3 embryo transfer | Transfer date + 263 days |
| Egg retrieval (fresh cycle) | Retrieval date + 266 days |
| IUI | IUI date + 266 days |
The American College of Obstetricians and Gynecologists (ACOG) says to date an IVF pregnancy from the embryo’s age and the transfer date. Its own examples match the table: 261 days after a day-5 transfer and 263 days after a day-3 transfer. The other rows use the same 266-day count from fertilization. The IUI row assumes conception on the IUI day, so it can be a day or two out.
Frozen transfers and donor eggs
The sum is the same. A frozen embryo’s age is the age it reached before freezing, so a frozen day-5 blastocyst counts as day 5 on transfer day. With donor eggs, use the embryo’s age too. The donor’s age and cycle don’t change the date.
Implantation after a transfer
In a natural pregnancy, the embryo implants 6 to 12 days after ovulation, most often on days 8 to 10. An embryo transferred on day 5 is about 5 days past ovulation. So implantation most often happens 3 to 5 days after a day-5 transfer, or 5 to 7 days after a day-3 transfer. The calculator shows days 6 to 10 past ovulation, which covers most pregnancies that continue. Many people feel nothing at all, and that’s normal.
When to test
Your clinic will book a blood test for the pregnancy hormone hCG, often called the beta. It’s usually about 9 to 14 days after the transfer, depending on the embryo’s age and your clinic. Home tests taken earlier can be misleading. The trigger shot used in many IVF cycles contains hCG and can show as a false positive, and an early negative can turn positive a few days later.
What comes after a positive beta
- A second beta a few days later, to check the level is rising.
- A first ultrasound at about 6 to 7 weeks, often at your fertility clinic.
- A hand-off to your obstetrician or midwife, often around 8 to 10 weeks.
Your clinic’s own schedule comes first. These are typical ranges, not rules.
Sources
- American College of Obstetricians and Gynecologists, Committee Opinion 700, “Methods for Estimating the Due Date” (2017). acog.org
- Wilcox AJ, Baird DD, Weinberg CR. “Time of implantation of the conceptus and loss of pregnancy.” New England Journal of Medicine, 1999. nejm.org
- American College of Obstetricians and Gynecologists, Committee Opinion 579, “Definition of Term Pregnancy.” acog.org
- CDC, “Tdap vaccination during pregnancy” and “RSV vaccine for pregnant people.” cdc.gov, cdc.gov
- Khambalia AZ, et al. “Predicting date of birth and examining the best time to date a pregnancy.” International Journal of Gynaecology and Obstetrics, 2013. Only 5% of births fell on the due date. doi.org