Due date variation

[LunaDreams]

Hi all,

I'm just wondering what way most people measure their due date?

I'm very confused and getting myself in a right pickle. My cycle length is usually around 31 days but can vary. I have no idea when exactly I ovulated as had EWCM for about 6 days mid cycle and had unprotected sex towards end and just after this. Then had my BFP day 30 of that cycle.

I downloaded Ovia app which put me at 6 weeks on friday. I had a scan which didnt show much and they questioned my dates. I've since looked at lots of different due date calculators and some put me at 5 weeks 6 today (would have been 5+4 on my scan day). NHS one just says 5 weeks!

I'm confused about why they all give such different answers. I know they cant tell exactly but even when putting in the same information (date of LMP) why do they vary so much?

@LunaDreams
I would forget about your own calculations now, as there is so much to consider. And instead just go by the NHS's dates, as that's the date that will follow you on the journey. X

Until you have your dating scan at 12 weeks the NHS will use you LMP on a 28 day cycle. When my dating scan was done I jumped forward a few days which fitted with what I had first suspected my date to be. Good luck with your pregnancy

Go by your last period date until your NHS 12 week scan. They’ll give you an updated due date then.

It doesn’t really matter, because when they do your dating scan (aka 12 week scan, but it’s not always 12 weeks) the due date estimated from the size of baby at that scan is the one they’ll use for everything going forward regardless of dates.

The NHS one doesn't show days so just says 5 weeks or 6 weeks or whatever.

They're all showing roughly the same. Around 5.5-6 weeks. They can only predict based on the information you give, adjusting for cycle length sometimes if they ask for that info.

It's all moot really once you have a clear scan.

Thanks for your replies.

To add a bit more context I'm trying to figure this out as I was told at my scan last Friday that I'm either earlier than I thought, or have miscarried.

I guess I'm trying to cling onto hope that I am earlier than 6 weeks to explain why they couldn't see yolk sac or embryo on scan.

Maybe I just need to go by NHS calculator which puts me at 5 weeks and keep everything crossed for next scan

When did your last period start, when did you have sex and when did you test positive?

@LunaDreams
I get it now, you poor thing, what a worry.
If it helps, I thought I was 7 weeks and turned out I was 5 weeks (which is bizarre as I knew my ovulation date). But it meant I saw nothing at the scan and instead had to go back 1.5 weeks later. It's a horrible wait, but better to wait & be certain, than guess X

@ShowOfHands my LMP was on Christmas day (I know right )
Had sex on 9th, 10th & 13th Jan then got my first positive on 23rd Jan. EWCM was between 6th & 11th so I presumed I ovulated around 12th but not sure.

@cat709 I'm sorry you experienced this agony too but I'm very glad you had a positive result :)

I'm tying to stay positive but finding it hard when the nurse in EPU gave me a number to ring in case of heavy bleeding and pointed me to the Misscarrigae Association website if I wanted more info! Those words haunt me when trying to be positive!

@LunaDreams
Yeh there is definitely limited TLC in the early stages from hospital/midwives. It feels so factual. Just try to keep busy and fingers crossed for your next scan x

Due dates vary wildly at such early stages. Your "estimated" due date is always worked out by LMP initially but it presumes you ovulate bang on 2 weeks later, most don't. Babys grow to a similar size around the dating scan so that will be where your official due date will be established.
Our eldest they brought her due date forward at her dating scan but by the anomaly scan her growth was in line with lmp, they stuck with the dating scan date though. My twins measure 6 days behind on an early scan but caught up to lmp by their dating scan. Our other 2 have measured in line with lmp at dating scans. Current I'm 12+1wk and have my dating scan in 2 days, will soon see if growth is in line with lmp or not.

If you conceived around the 12th, you're still under 6 weeks. If they are recording your lmp as Christmas Day, they're expecting you to be a week further on than you actually are.

As strangers on the Internet, we can't tell you things will be okay sadly but from your dates of having sex, ewcm and your positive test, you're just a week behind what your lmp suggests.

I know how hard it is to stay positive. I've been there and had it go both ways.

(I had a period start on Christmas Day 2020 too, seemed to sum the year up tbh)

I have 30/31 day cycles. The online calculators tend to give you dates based on a 28 day cycle, which doesn’t help. Some let you put in your cycle length too, and even then it gives me dates that align with a 28 day cycle. It’s very confusing!

On top of that, it’s also dependent on when you conceived, which is obviously hard to tell.

I think it’s also important to remember that 6 weeks itself is still borderline early to be able to see anything, so that, combined with uncertainty re dates means it is possible that the scan was just too early. Fingers crossed!