How IVF pregnancy dating works
Unlike natural conception where the precise moment of fertilization is uncertain, assisted reproduction dates pregnancy with exact chronological certainty.
For a Day 5 blastocyst transfer, the embryo is already 5 days old (equivalent to day 19 of a standard 28-day cycle). Delivery occurs exactly 261 days after transfer.
For a Day 3 cleavage-stage transfer, delivery occurs 263 days post-transfer. For egg retrieval or intrauterine insemination (IUI), delivery is 266 days later.
Worked example: Day 5 blastocyst transfer
An embryo transfer occurs on October 15th with a 5-day frozen blastocyst.
Calculation: October 15th + 261 days = July 3rd of the following year.
On the day of transfer, the patient is clinically 2 weeks and 5 days pregnant (19 days of gestational age).
IVF transfer inputs
Transfer Type
Choose Day 5 blastocyst, Day 3 embryo, Day 6 blastocyst, or egg retrieval.
Date
Date the procedure was performed.
CALCULATOR QUESTIONS
IVF embryo transfer due date calculator questions
Is a Day 5 blastocyst due date more accurate than LMP?
Yes. An IVF due date is the single most accurate delivery date in obstetrics because the exact fertilization and development time of the embryo is documented.
When is the first ultrasound scheduled after IVF?
Fertility clinics typically schedule an initial viability ultrasound between 6 and 7 weeks of gestational age (around 3 to 4 weeks after a Day 5 transfer).