To ask for your help explaining this to my boyfriend?

[ufgh]

So, I'm trying to explain to DP about due dates and the fact they're calculated from your last period.
We know full well I conceived 2.5 weeks after that as we hadn't slept together for ages before that.
So now he's confused that we slept together and conceived say 12 weeks ago but baby is measuring 15 weeks.

How do I explain this?

And when I say "baby" I actually mean "collection of cells"

We’ve always used date of last period.
The reason being that, as most couples are having sex more than once a month, and ovulation doesn’t reliably occur exactly mid cycle, there’s usually no way to tell the date of ovulation.

I get that it seems a bit weird but it’s not that hard to grasp. Does he understand it’s based on a woman’s cycle? That conception is a process rather than just the shag? Does he know how long it takes for implantation to happen etc? Or that ovulation could be a few days after sperm turns up?

In terms of trying to persuade him, I'd agree with him that it is a weird system. If I was only just finding out about it, I think I'd be kicking up a fuss because it's illogical. And I'm that sort of person.

It’s not the age of the egg either! Baby girls are born with all their eggs already present in their ovaries. We simply release one of them per month.

It’s dated from the start of a period because it’s impossible to know the exact date you ovulated, even if you were tracking your cycle which most women do not. It’s just the easiest dating method until the first scan which can throw the dates off by a few days or even weeks in some cases.

If you’re 15 weeks pregnant, you probably conceived 13 weeks ago but that’s not a definite because some people have irregular cycles and can ovulate late.

Just show him an article about it and tell him to pipe the eff down.

The age of the EGG? Why the fuck would any medical professional refer to the age of the basic building block before it changed functions? And not the age of the actual human growing inside you?

Say that it started that way before there were scans, so you only had period dates to go by. They never changed it once biology knowledge increased as it would confuse all the "facts," like weight charts etc.

If he's going on and on about it, tell him that a) google will confirm this is the way it's done b) yes other people think it's a bit silly too and c) can he now STFU because he's getting tedious about it.

(I'm one of those who knew when in the month DS was concieved - at least two weeks later than the 'official ' date, because I only had sex on one date that month.)

If this is part of a larger pattern of controlling, nitpicking, nagging and insistence that you are having sex with other men, you might want to think about getting rid of him sooner rather than later.

Maybe think of it like this. It's the age of the egg. Say, egg is released on the first of the month. It's met by sperm and fertilised on the 15th. Come the 30th you had sex 15 days ago but the egg was released 30 days ago. So the egg is 30 days old. And that's how your pregnancy is dated. It goes by your last period, when the egg was released, how old the egg is.

(I know - a period isn't when the egg is released but it is right before the next one comes so probably the best way of determining the start the ovulation.)

None of this makes any sense. I'm getting a bit glad that I didn't have to cope with any of this shit because I'd probably have had a massive ruck with nurses/doctors/magicians

Assuming he isn't trying to suggest you've been with someone else I would have one more go at explaining it, if he still doesn't get it then simply say 'I don't know why, that's just how they do it, let's just focus on getting ready for it shall we° you might also remind him that' full term ' varies from country to country. In France I believe its 41 weeks, in the UK 40, but anything 38 on is basically full term so it's not an exact science.

He says he 100% believes me and trusts me and he's not saying anything in a nagging or controlling way, he just seems genuinely confused - and I keep bringing it back up because I can't fathom how he just can't understand it!!

In honesty I don't particularly understand it and I've had a baby! Although in this case it seems he is probing not as he is wanting to learn more about the miracle of life, but as he is distrustful. Tell him to go online and look it up, there must be tonnes of stuff about it.

I don’t think he’s being dense at all, I don’t understand it either. It’s not an embryo until it’s fertilised, it’s just an egg, so it seems logical that timings start at the point of conception/fertilisation

I agree about telling him to google it though, you have better things to do I’m sure!

@RandomAmanda that's a good way to explain it!!

Maybe stop 'bringing it back up' then?

You've got issues with this bloke, it stands out a mile

@BatFacedGirl why? I'm just trying to explain something that he doesn't understand considering it's something we're going through at the minute?

Sorry I mean the age of the egg since it matured and left the ovary - that being the start of the cycle. The reality is that it’s complicated and the more you know the more your mind is blown. That egg having been around since you were in the womb. I have twins and the biology of that is really mind blowing

Random I appreciate you trying but that is NOT how egg release works.

When you're infertile you learn this shit off by heart, believe me.

OP sorry I didn't mean to derail your thread. I'll fuck off now.

I wouldn’t know about this, I’m a middle aged woman with four kids, none of whom are my biological children.
I’m with Furious.

My DP spent first 20 weeks insisting on using his own counting system from conception not last period even though i explained the convention to him, he just said well i am counting from this date. He has just started adapting to same dating as everyone else... maybe just leave him to it.

It is weird. But there’s no other way to date it to the precise shag, particularly as sperm can stay alive inside a woman for up to 7 days after that I think, so actual conception can vary. So it’s a convention.

The foetus isn’t actually 2 weeks old when conception occurs, this is just the convention for dating.

A bit like leap years. A real solar year isn’t exactly 365 days but we have the convention of a calendar so every four years we add a day to make the calendar and solar year’s match. It just makes stuff easier.

Babdoc’s explanation makes sense. It’s purely down to trying to find a consistent point to measure from rather than actually havin anything to do with the ‘age’ of the foetus?