How long is a pregnancy actually? AIBU to be so confused at this?

[WhatTheActualFuuu]

Name changed for this because it's possibly the stupidist question in AIBU history.

I don't have kids (I'm on MN for the life advice and laughs) and I've honestly always thought a pregnancy is 9 months.

But then I see posters talking about being early at 38 weeks, and referring to being 40 weeks pregnant.. I thought a pregnancy was 9 months, so 36 weeks?

AIBU to utterly confused?

I know this is totally irrelevant to me at this point but I just cannot work it out!

Another stupid question what's the 40+8 mean?

Once you get to 40 weeks you usually stop adding weeks as you go overdue. So some people say 40+9 rather than 41+2. As the "normal" pregnancy length of 40 weeks is over. A bit like extra time in football - the main clock stops at 90 and another little clock adds the extra minutes.

I'd take 40+8 to mean 40 weeks and 8 days, so really a week over due.

Just to throw I some additional confusion. The UK medics class 40 weeks as full term. 75% of first babys are over due. France class 41 weeks as full term and dont have so many go over due. That was info I found out when I was trying to work out my odds of avoiding being induced.

Only 5% of babies are born on their due dates. The whole 9 months/40 weeks thing is just a very rough guide. We need this rough guide because if you give birth too early, your baby may not be developed enough to survive outside the womb, and if your pregnancy goes on too long your placenta might stop working and the baby might die. So they don’t tend to like women going over 42 weeks or under 37 weeks because, statistically, it is more dangerous. But in actuality, the vast majority of women will give birth between 37-42 weeks, and only 1 in 20 will give birth on their actual due date.

Counting down the last three weeks I can confirm this meme is 100% truth.
Also that's fascinating that there's a difference between ethnicities as to what's average, I did wonder why, if 75%+ go over 40, we would consider that a due date! Must be a north Western Europe bias. There's a big Swedish study that put their average around 41+2 or close to that.