Sorry, I have tried googling but am a bit confused.
I know that weeks one and two are before ovulation so pregnancy dated from first day of last period.
So if the first day of last period was 8 weeks ago to the day, you are 8 weeks.
BUT if a book is describing pregnancy in terms of 'week 8' or 'week 9', how exactly does that work? When you reach the date of 8 weeks as above, are you just starting week 8 or have you just finished it?
I suspect this may be a silly question, I have a mental block here maybe!