Frozen Embryo Transfer (FET) Due Date Calculator
Enter your transfer date and embryo age to estimate your due date, equivalent LMP, and milestone dates.
Medical disclaimer: this tool provides an estimate only and does not replace guidance from your fertility specialist or OB-GYN.
How a due date is calculated after frozen embryo transfer
A standard pregnancy due date is based on 40 weeks (280 days) from the first day of the last menstrual period (LMP). In IVF and frozen embryo transfer cycles, your clinic knows the exact embryo age at transfer, so we can estimate gestational timing more precisely than with natural conception estimates.
The core idea is simple: a pregnancy is typically dated as 266 days from fertilization, or 280 days from LMP. If your embryo is already 5 days old at transfer, then your transfer date is effectively equivalent to gestational age 2 weeks + 5 days.
FET due date formula
Use this formula:
- Estimated Due Date (EDD) = Transfer Date + (266 − Embryo Age in days)
- Equivalent LMP = Transfer Date − (Embryo Age + 14 days)
| Embryo Age at Transfer | Days to Add to Transfer Date | Typical Use Case |
|---|---|---|
| Day-3 embryo | 263 days | Cleavage-stage transfer |
| Day-5 embryo | 261 days | Most blastocyst transfers |
| Day-6 embryo | 260 days | Blastocyst transfer |
| Day-7 embryo | 259 days | Less common blastocyst transfer |
Why IVF dating is often more accurate
In spontaneous conception, ovulation and implantation are estimated. In IVF/FET, the embryo development day and transfer date are known. That often makes early pregnancy dating highly reliable, especially before a first-trimester ultrasound confirms growth.
Does a frozen transfer change due date reliability?
Not really. Whether an embryo is fresh or frozen-thawed, due date math uses embryo age and transfer date the same way. The freeze process does not add or subtract gestational days.
Important milestones after FET
Many patients want more than one date. Here are common milestones used in IVF pregnancies:
- First beta hCG blood test: often around 9-11 days after transfer (clinic protocols vary).
- Early ultrasound: frequently around 6-7 weeks gestational age.
- End of first trimester: 13 weeks + 6 days.
- Anatomy scan window: roughly 18-22 weeks.
Example calculation (Day-5 transfer)
If your frozen transfer date was March 1 and you transferred a Day-5 embryo, add 261 days. That gives an estimated due date in late November. Your equivalent LMP would be 19 days before transfer.
Frequently asked questions
Is my due date exact?
No due date is exact. It is a best estimate. Many births happen between 37 and 42 weeks, and your care team may update dating after ultrasound.
Does PGT testing affect due date?
No. Genetic testing status (PGT-A/PGT-M/PGT-SR) does not change pregnancy dating calculations.
Can I use this for donor egg, donor sperm, or gestational carrier cycles?
Yes. If you know the transfer date and embryo age, the due date formula is the same.
What if I am not sure whether my embryo was Day-5 or Day-6?
Ask your clinic for the exact embryo stage listed in your transfer report. A one-day difference in embryo age changes EDD by one day.
When to call your fertility clinic or OB provider
Contact your care team for any bleeding, significant pain, fever, or symptoms that worry you. Online calculators are useful for planning, but your medical providers should guide diagnosis, monitoring, and prenatal care.
Bottom line
A frozen embryo transfer due date calculator is one of the most practical IVF tools for planning prenatal visits, maternity leave, and milestone expectations. Start with your transfer date and embryo age, then confirm everything with your fertility clinic.