How the IVF due date is calculated
A pregnancy lasts about 266 days from fertilisation. After IVF, the day of fertilisation is known exactly, so the due date can be worked out precisely:
- From a day 5 blastocyst transfer: transfer date plus 261 days
- From a day 3 embryo transfer: transfer date plus 263 days
- From egg collection: collection date plus 266 days
Pregnancy weeks are counted from two weeks before fertilisation, the same way as a natural pregnancy is dated from the last period.
How accurate is it?
IVF due dates are among the most accurate, because the timing of fertilisation is known. Even so, only a small share of babies arrive on the due date itself; most are born in the two weeks around it. Your doctor will confirm the dates with an early ultrasound.
After a positive pregnancy test
Continue the medicines your doctor prescribed until told to stop. The first ultrasound is usually done two to three weeks after a positive blood test, to confirm the pregnancy and see the heartbeat.
Questions
Is the due date different for a frozen embryo transfer?
The calculation is the same. What matters is the age of the embryo on the day it was transferred, not when it was frozen.
How many weeks pregnant am I at the time of transfer?
On the day of a day 5 blastocyst transfer you are counted as 2 weeks and 5 days pregnant; for a day 3 transfer, 2 weeks and 3 days.
When should I do the pregnancy test after IVF?
A blood test (beta hCG) is usually done 9 to 11 days after a blastocyst transfer. Home urine tests taken earlier can be misleading.