IVF due date calculator
Enter your embryo transfer date, IUI date or last period to calculate your estimated due date. Works for day 3 transfers, day 5 blastocyst transfers and natural conception.
How IVF due dates are calculated
A standard pregnancy is 280 days (40 weeks) from the first day of the last menstrual period (LMP). With IVF, the exact moment of fertilisation is known, so the calculation works backwards to find the equivalent LMP date.
For a day 5 blastocyst transfer, the embryo is already 19 days past the equivalent LMP (14 days of a hypothetical cycle + 5 days of embryo development). So the due date is 280 minus 19 = 261 days from transfer.
For a day 3 transfer, the embryo is 17 days past equivalent LMP, so the due date is 263 days from transfer.
Because IVF dates are precise, these estimates are typically more accurate than natural conception due dates, where the exact ovulation date is often uncertain.
Frequently asked questions
How do you calculate an IVF due date?
For a day 5 blastocyst transfer, add 261 days to the transfer date. For a day 3 transfer, add 263 days. For IUI, add 266 days to the insemination date. These calculations align the IVF pregnancy with a standard 280-day pregnancy counted from the last menstrual period.
Is an IVF due date different from a natural conception due date?
The due date itself is the same — 40 weeks from the equivalent last menstrual period. The difference is that with IVF, the conception date is known precisely, so the estimated due date is more accurate than one based on a reported last period.
How accurate is an IVF due date calculator?
IVF due dates are more accurate than natural conception estimates because the exact date of fertilisation is known. However, only about 5% of babies arrive on their exact due date. Most are born within two weeks either side. Your dating scan at 7-12 weeks may adjust the estimate slightly.
When is the first scan after IVF?
Most UK fertility clinics schedule the first scan at 6-7 weeks of pregnancy (approximately 2-3 weeks after a positive pregnancy test). This early viability scan checks for a heartbeat and confirms the pregnancy is in the correct location.
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