Can anyone answer my silly question

[Tea1Sugar]

Full term is 37+ weeks. So why if a baby is born early, at say, 34 weeks are they said to be 6 weeks premature, not 3 weeks?

40 weeks is the average length of pregnancy. A baby born at 34 weeks is born 6 weeks earlier than average. Three weeks earlier (37 weeks) isn't a significant deviation from the average and such babies do not tend to have difficulties associated with prematurity.

I was thinking the same thing....

Because everything is measured at 40 weeks gestation. Which is in itself bonkers because that is measured from the first day of your last period. So for at least 2 of those weeks you weren't actually pregnant as you hadn't even ovulated yet.