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!

Not all months are 4 weeks so 40 weeks does work out to be 9 months, for example some months have 4 weeks and 3 days etc

It is 9 months but because there arent always 4 weeks to a month it doesn't work out 36 weeks. Most months have longer.

Plus they add 2 weeks on to the beginning as they date it from the first day of your last period.

Pregnancy is 40 weeks, but counted from the date of your last period, which is usually about 2 weeks before you actually conceived. So you are only actually pregnant for 38 weeks even if you deliver at 40 weeks gestation.

And confusingly they count weeks from last menstrual period. Not from date of conception.

As others have said they add 2 weeks on, so you’re 4 weeks when you’re really physically 2, and some months are 5 weeks and some 4, so it’s a bit messed up!

38 weeks actual pregnancy, plus the 2 weeks they tack on so you count from your last period. That is an average. There are also variations by ethnicity (Im sure someone will want to argue) archive.is/jQBMg

Conclusions This research suggests that normal gestational length is shorter in Black and Asian women compared with white European women and that fetal maturation may occur earlier. Source study of 122,000 spontaneous labours

Normal term of pregnancy is 37-42 weeks, but counted frkm date of last menstrual period, so you are already 2 weeks pg at date of conception.

Pregnancy due dates are normally calculated on 280 days (40 weeks) from the first day of the last period.

the average month is 30.4 days long, not 28.

9x30.4 is 274 days, 10*30.4 is 304; So 9 months is much nearer than 10.

Talking in weeks is more accurate than months really so weeks are used for medical reasons not months
I think the whole 9 months thing is an older throwback when they didn’t talk in weeks!

Really? You dont get that months are mainly more than 4 weeks?

Three month is 13 weeks not 12. So 9 months is 39 weeks not 36. Also confusingly pregnancy is dated from your last period even though on average women ovulate 14 days after. Hence when you are 4 weeks pregnant you actually convicted 2 weeks ago

Well a month isn’t 4 weeks (except February, most of the time) so 9 months isn’t 36 weeks for a start:

Also, hardly anyone gives birth on their due date. DH (despite being a v bright man) was astounded when I explained this 😂

Did you not realise a month is not 4 weeks ? Really ?

3 months is 91/92 days =13 weeks. Due date is normally calculated as 9 months and 1 week from first day of last period.

@Holdthedamndoor I know a month isn't four weeks, but I've never really heard of the term of a pregnancy in terms of months (so 9 months not 40 weeks). Generally I do think of a month as four weeks though, yes.

Well you're not completely wrong op cause 9 months isn't 40 weeks is it?

Nothing to do with not being a mother, you are totally unreasonable not to know that 4 weeks does not equal 1 month, do you really not know how many days are in each month?

I'm sure I read a thread about this in the last couple of days and was surprised that thinking a month was 4 weeks was a thing as I'd never heard of anyone who isnt aware of that but it seems I was wrong, there are people who have somehow missed that bit of basic knowledge.

Don't you know anyone with birthdays on the 29th, 30th or 31st of a month - how did you think that worked?

To be honest I’ve been pregnant and I still don’t really get the months thing

I know a month isn't four weeks exactly.

I've never had reason to stop and wonder about the length of a pregnancy though and thought I'd ask here.

I'm not stupid. Thanks to those who have explained.

It is dated from the first day of your last monthly period. I believe that is because that is the only date that many people are actually likely to know. Nobody can really know for sure the date that they actually conceived, although in the majority of cases it will be about two weeks after the first day of their last period.

Pregnancy itself lasts about 38 weeks, so the easiest way to date it is to count 40 weeks from the first day of your last period. That gives you your estimated delivery date.

^^^ they all explained it lol BUT I’ve friends who asked this as I was the first to have a baby, so it’s something lots of people wonder I believe but don’t ask. Remember- there’s never a silly question!

Generally I do think of a month as four weeks though, yes

But it’s not 🤷🏻‍♀️. So that’s why 9 months doesn’t equal 36 weeks.

@SnowyAlpsandPeaks thank you! I feel much less of an idiot now :)