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About

In Vitro Fertilization (IVF) pregnancies require a different calculation method than natural conception. Using the 'Last Menstrual Period' (LMP) is notoriously inaccurate for IVF because medication often manipulates the ovulation cycle. To get a precise Estimated Due Date (EDD), you must calculate based on the exact biological age of the embryo at the moment of transfer.

This tool adjusts the timeline based on your specific procedure—whether it was a Day 3 embryo transfer, a Day 5 blastocyst transfer (FET), or an Intrauterine Insemination (IUI). This precision reduces anxiety and ensures your medical milestones align with the baby's actual development.

ivf calculator due date by transfer fet calculator day 5 transfer infertility tools

Formulas

The formula standardizes the pregnancy to a theoretical 280-day cycle (40 weeks) by adding the remaining gestation time to the transfer date.

EDD = DateOfTransfer + (266 EmbryoAge)

Example: For a Day 5 Transfer, we add (266 - 5) = 261 days.

Reference Data

ProcedureCalculation LogicAvg Days to Birth
Natural / IUIOvulation Date + 266 Days266 Days
Egg RetrievalRetrieval Date + 266 Days266 Days
Day 3 TransferTransfer Date + 263 Days263 Days
Day 5 Transfer (Blast)Transfer Date + 261 Days261 Days
Day 6 TransferTransfer Date + 260 Days260 Days

Frequently Asked Questions

In natural pregnancies, ovulation is estimated to be Day 14, but can vary wildly. In IVF, the exact moment of fertilization (or retrieval) is known to the hour. This eliminates the 2-week estimation window used in standard calculations.
For FET, use the 'Day 5 Transfer' option (most frozen embryos are blastocysts). The date the embryo was frozen does not matter; only the date it was transferred into the uterus counts.
A clinical pregnancy is confirmed when a heartbeat is detected via ultrasound, usually around Week 6-7 (approx. 4 weeks after transfer). Positive blood tests (Beta hCG) confirm a chemical pregnancy earlier, around 9-14 days after transfer.