When is your baby due?
There are around 266 days between fertilisation and the birth of your baby. The first day of your last period is used to calculate your due date because the time that sexual intercourse took place does not have to coincide with fertilisation.
Important to know: A normal, 'on-schedule' full-term birth can deviate up to 2 weeks from the calculated due date. And deviations are the norm here: Only 5% of all pregnant women give birth on the calculated due date.