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Pregnancy

Talk about every stage of pregnancy, from early symptoms to preparing for birth.

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Original poster

DP doesn’t understand LMP dates

27 replies

Apprehensiveone · 03/05/2018 23:15

Dp and I had ‘a break’ in February (very important) it was short lived (a month) and we sorted things out... last week, I took a preganacy test and it was positive. Was fully expecting that because my Lmp started 8/3/18... we’re not trying for a baby but also not really using condoms correctly (spur of the moment, no condom..) knowing this is our approach to contraception I’m half expecting this.... so last night I told dp I’m pregnant and he’s actually okay with it. We spent the whole night chatting about what was to come and how exciting it all is, i woke up this morning feeling so happy!! Today I booked my first antenatal appointment and told dp it’s in a few days, he is happy and says he’ll be there. I mentioned that they said my 12 week scan is due at the end of May and not to worry because when they say I’m 12 weeks pregnant they really mean I got pregnant 10 weeks ago as they use LMP dates and he was instantly ‘you shagged someone else while we’re on a break and now you’re saying this child is mine’ ... well, no, that’s what’s going to happen isn’t it? They’re going to take my Lmp and add 2 weeks? He’s asked me to explain why they would do this and I’ve said it’s just what happens but he’s convinced I cheated on him. Don’t boys learn this in sex Ed? Why doesn’t he understand this?

OP posts:

Are your children’s vaccines up to date?

Set a reminder

Zcarter · 03/05/2018 23:27

My parter didn’t realise for the first 2 weeks of your pregnancy your not actually pregnant!!!!! Can you show him some literature explaining this or ask your doctor / midwife xxxx

Congratulations btw xxxxx

Wolfiefan · 03/05/2018 23:34

Sounds like the issues you thought you had sorted aren't really sorted out at all.

Smidge001 · 03/05/2018 23:37

I didn't know this until about half way through my first IVF treatment. I also didn't know they counted your cycle from the start of a period (I always assumed the period came at the end) and that day 1 is only from the first heavy day. As a result I went for an internal ultrasound smack bang at my heaviest point of the period as I counted from the first sign of spotting.

Anyway, my point being that as a moderately intelligent girl, I still can't understand why they would say you're 12 weeks pregnant when you're clearly only 10ish. So I don't really blame him for being sceptical. It really is a ludicrous measurement that makes no sense.

Imelda03 · 03/05/2018 23:50

I know this sounds a bit daft but I found it easier to explain to hubby with a calander on the wall showing hypothetical ovulation and fertilisation dates but highlighted day 1 of LMP and explained they use this date as the begining of the 40 wk count down. Might be worth getting midwife to explain to or GP? X

Hope you get this sorted soon though as you really want to enjoy this time being pregnant together x

GuntyMcGee · 03/05/2018 23:55

They use LMP to calculate a provisional estimated due date as women's cycles can vary in length. Counting day 1 of your period as the first day of bleeding makes sense as women can bleed for varying amounts of time. So you couldn't reliably count from last day of period. And most women have no idea when they ovulate, so you couldn't use that date either.

On average, ovulation occurs 14 days after first day of period, but not always and women vary in luteal phase (post-ovulation) length, so that couldn't be counted either.

So although women haven't conceived in those first two weeks because they haven't yet ovulated, a pregnancy is classed as weeks from LMP, because otherwise there is not set benchmark to calculate from.

Pregnancy is counted as an average of 280 days (40 weeks/10 months) from last menstrual period, however full term is seen as 47/42 weeks. So as you can see nothing is set in stone, it's all based on averages and you're not physically pregnant for the first two weeks of pregnancy because it's impossible to be as you won't have ovulated. But without use of LMP pregnancy wouldn't be able to be calculated at all.

Oh and to add to the confusion, your dates will most likely change again when you have your dating scan as the crown rump length of your baby will be calculated by an algorithm which takes into account the average of 280 days and the physical measurement of your baby. It's very complicated.

That aside, it sounds like you've got deep issues in your relationship that need to be worked out.

GuntyMcGee · 03/05/2018 23:57

37 - 42 weeks that should say

zaalitje · 04/05/2018 06:55

Try showing him on one of the due dates apps/ websites.
They all work with LMP

ShowOfHands · 04/05/2018 07:02

Explain to him that women have been having babies for millennia and before we had scans and Mumsnet, we just knew that it took around 40 weeks from our last period and thus has it ever been. And those 2 weeks are part of the pregnancy cycle because your body is prepping your uterus.

They can tell him when you conceived at the scan as well as you inputting the likely date of conception on a pregnancy app and showing him how it then calculates the pregnancy.

It's a bigger problem that he doesn't trust you.

Ohyesiam · 04/05/2018 07:04

Can’t he google it?

EventNotInData · 04/05/2018 07:06

www.nhs.uk/conditions/pregnancy-and-baby/due-date-calculator/
That’s the NHS site which he might find convincing.

This is a fact widely unknown by men. An ostentatiously “woke” but normally intelligent bloke on my social media feeds had a huge rant about how a new law in one US state had redefined pregnancy to start at LMP when women weren’t even pregnant and this was a terrible right wing conspiracy to restrict reproductive rights by making women look more pregnant than they really were!!!! A surprising number of men were equally shocked by those dastardly Republicans denying Science again.

I hope it works out for you OP.

EekThreek · 04/05/2018 07:15

In fairness, I didn't know this before my first pregnancy, so I don't think it's fair to berate men for not understanding it. And it looks like you haven't quite understood it either from your OP...

They're not going to take your LMP and add two weeks, they just count from your LMP. So if your LMP was 10 weeks ago and the scan shows you as 12 weeks, then it would suggest that you had sex with someone other than him. Or that you're growing a huge baby...

But if that was a slip of the fingers while typing, I apologise. If you meant you had sex with him 10 weeks ago, and the scan shows you at 12 weeks, that's slightly more accurate - but as others have said, that's not how they actually work it out.

Joinourclub · 04/05/2018 07:34

They’re going to take my Lmp and add 2 weeks?

I'm confused by this. Do you think that, or does he?

Cosmoa · 04/05/2018 10:15

My LMP due date was April 30th (so like 4 days ago) and my scan due date puts me at May 21st!!

It's not as simple as we would all hope when it comes to working out when you got pregnant!

Cosmoa · 04/05/2018 10:15

Although I know for certain the date we had sex to get pregnant as we didn't do it for like a month before or after 😂

Original poster

Apprehensiveone · 04/05/2018 12:11

Apologies for the confusion re ‘they’re going to take my Lmp and add 2 weeks’ no idea why I put it like that (I’d got into the rant by then and wrote something that makes no sense is my only excuse )

Those saying we appear to have ‘issues’ yes I agree. The fact he just came straight out with that rather than ‘oh, how weird, I’ll have to look that up’ or something has me worried. I’m trying to stay upbeat though because I really want to enjoy my pregnancy, I’m so excited to become a mother! I just wish we could be excited together. At the moment he’s just replying normally to my texts (we don’t live together) and hasn’t mentioned it since. Perhaps he’s looked it up. I don’t want to raise the subject again until our appointment and I’ll get the medical professional to explain!

OP posts:

steppemum · 04/05/2018 12:23

I think the simplest thing is to explain one cycle.

day 1 of period,
day14 ovulation, get pregnant/not get pregnant

can't usually get pregnat between 1 and 12 (ish) , don't usually get pregnant between about days 17 and 28.

So the only person who can make you pregnant is the one you slept with on those days.

Poptart4 · 04/05/2018 15:28

The only way to fully end his doubt is to get a DNA test. I know your sure he's the father but this will end him throwing accusations at you every time you have an argument.

They can do DNA tests while your still pregnant through a blood test. Ask your doctor about it.

Liz3891 · 04/05/2018 16:36

Yes, think of your pregnancy as a cycle like steppemum said. In a normal cycle your period is day 1. In a pregnancy cycle, your period is day 1.

BlueBug45 · 04/05/2018 18:26

@Apprehensiveone he may of looked it up, but part of the problem with the literature is they always use the average cycle length of 28 days. If your individual cycle is shorter or longer, then you will ovulate either earlier or later.

For example I tracked my periods and when I ovulated for nearly a year and discovered I ovulated between anywhere between 8 and 18 days on my cycles. However my cycles aren't the same length and haven't been since I was around 20.

Anyway your OH is being an a-hole.

BlueBug45 · 04/05/2018 18:30

I forgot to add if you use the day 14 of your cycle as the day you ovulate - which many couples TTC do use - then you find you can't get pregnant. This is why your individual cycle is important for conception.

WomanEqualsAdultHumanFemale · 04/05/2018 18:33

I mentioned that they said my 12 week scan is due at the end of May and not to worry because when they say I’m 12 weeks pregnant they really mean I got pregnant 10 weeks ago as they use LMP dates

I find it odd that you would say this. It’s like you were getting it in before he could question it. Like you expected him to be suspicious?

thenewaveragebear1983 · 04/05/2018 18:39

At all of my scans they have given a due date but also given an approximate date of conception or number of weeks/ days since conception as well as saying ‘13 weeks pregnant’. You could always ask the sonographer to tell you how many days/weeks they estimate since conception at the scan. In my experience after that first scan no one asks when your LMP was because the scans are so accurate and not everyone has exactly 2 weeks from LMP to conception.

The fact that your dp doesn’t believe you, is a whole different issue!

BlueBug45 · 04/05/2018 18:44

@WomanEqualsAdultHumanFemale not really odd if you are explaining it to someone who isn't aware of this stuff.

AnotherOriginalUsername · 04/05/2018 18:47

I downloaded the Ovia pregnancy app after using the Ovia fertility one whilst TTC. It shows what's going on each week of pregnancy and shows week 1 as your period, week 2 as ovulation, week 3 fertilisation etc. Would showing him something like that help ?

WomanEqualsAdultHumanFemale · 04/05/2018 18:54

I think it’s odd that she said “not to worry”. Why would he worry?

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