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Could somebody give me a little help with my dates please :)

(12 Posts)
confused91 Sat 10-Nov-12 10:53:54

right, long story short i am now nearly 26 weeks pregnant.

due on the 20/2/13.

i couldnt remember if i had my period in may of this year, if i did it would have been in the last week of may, i had my ultrasounds dating me etc, just wondered how accurate they are, as my dates dont add up, if they are right then it means i would have concieved within a week or so of having my period.

but what i need to know with all the dates etc more than anything is that even thought i have looked and worked it out thousands of times, that i wont have concieved on the 24th april, as on this date me and my partner had split and i slept with a friend. sad i love my partner to bits, we sorted out our differences and from what i can tell this baby cant be his as theres 3 weeks or so in between when we slept together and the dates i apparently would have concieved (poss around 30th may to 6th june) im probably just being really paranoid etc but i cant even put into word how much it means to me for my partner to be the babies daddy. i know this is confusing but i just need some reassurance off a few people, i dont feel like i have anyone to turn to now and im not enjoying my pregnancy at all because of this. i cant remember if i had a period before of after sleeping with my friend either. its just one big mess and im really down about it all.

if i put my EDD in a calculator thing for conception then it says my LMP would have been around 16th may, which cant be right it would have been at the end of may. does this make much difference to my dates etc?

sorry its all so confusing. thank you to anyone who takes the time to reply x

potatolady Sat 10-Nov-12 12:01:02

The most common date of conception is day 14, so on day 1 your period would start and on day 5-6 your oeriod would be finishing.
On that day (day 14) you would be considered 2 weeks pregnant as the weeks are calculated froim the first day of your period.

This is the average but there is obviously a lot of variation.

The scan dates are more likely to be correct than the calculation back from your due date. I think scan dates are correct to within a few days so give/take 5 days max.

My scan date this time means that I must have conceived on the last day of my period (so 8 days earlier than I thought) which is extremely unlikely so I am expecting my baby to be a few days later than EDD - have to wait and see tho.


stinkinseamonkey Sat 10-Nov-12 12:04:33

"if i put my EDD in a calculator thing for conception then it says my LMP would have been around 16th may, which cant be right it would have been at the end of may"

lots of people (me included) don't ovulate anywhere near day 14, so by my real dates (based on scan and known ovulation date) my period in those calulaters would be a totally different time to when it was IYKWIM

wanderingalbatross Sat 10-Nov-12 12:14:59

I think it's perfectly possible to have had your period a week later than the 16th May and ovulate a week early, and have a due date of 2nd Feb. Plus I think there is some variation in how long implantation takes, and some error in the scan date, so I think it's perfectly reasonable to imagine that you had a period at the end of May and then conceived. I can't see how you'd have a due date of 2nd Feb from sex on 24th April, as even with all the errors your due date would have to be a month or so earlier.

wanderingalbatross Sat 10-Nov-12 12:23:26

Sorry, meant can't see how you'd have a due date of 20th Feb!

Put another way - if you had sex on 24th April, sperm can survive up to a week, so your latest date for conception is 30th April. If that were the case, you'd have a due date of 22nd Jan. Even with some error for scan date and implantation, you'd still be looking at an early Feb due date, not a late Feb one.

confused91 Sat 10-Nov-12 13:33:37

I had an early scan dating me at 9+4 giving me an EDD of the 22/2/13 then had a re scan at 12 weeks which they then dated me properly and took my EDD back by 2 days. i know ultrasounds are pretty good with dating etc and surely it would be obvious in some way if i was further along. i know its a bit pointless etc im just such a worrier! we all make our mistakes and i'll love my little bab no matter what. just needed a bit of reassurance, thank you for all of your replies everyone x x

Havingkittens Sun 11-Nov-12 03:51:16

They date by size when you have an ultrasound so it may not necessarily tie in with your calculations according to your last period. I've had a few scans so far due to previous miscarriages and each time I measure a day or couple of days ahead of what I thought. My EDD has changed from 13 April to 9 April so far based on scans and that's as it stood at my 16 week scan. It may change again next time!

ZuleikaD Sun 11-Nov-12 06:23:10

The ultrasounds will be the most accurate. Foetuses are very predictable size-wise in the early weeks and they can be precise about how far along you are. If your EDD from the scan is 20th Feb then work back from there. BUT - remember that the number of weeks isn't from date of conception - for example if you were calculating EDD on dates then you would count 40 weeks from the first day of your last period. You wouldn't actually have conceived then, you would have conceived a couple of weeks later. So roughly speaking you are likely to have conceived between 15th and 30th May, as you've been told. You may have had a small implantation bleed at the end of May which might have confused things, but your last period was probably at the end of April.

rogersmellyonthetelly Sun 11-Nov-12 11:37:54

It does depend very much on when you had your scan. I had ivf for this pregnancy and know to the hour when conception occurred. At my first two scans at 7w and 9w the baby measured bang on for my dates. By 12 weeks she was 3 days behind. By 20 weeks she was 2 weeks in front, and at 26weeks she was measuring to within a couple of days of my dates.
With ds and dd I again I knew when I conceived, even though they weren't ivf, and at the 7w scans both were right on, but by 12w they were both measuring a week ahead, and still were at 20weeks.

rogersmellyonthetelly Sun 11-Nov-12 11:38:41

Basically, the early scans are likely to be most accurate, but even by 12 weeks they can be slightly out.

Pritchyx Sun 11-Nov-12 12:14:04

I'm apparently 13+5, and the dates I worked out was 18/5/13 (my birthday), midwife said 16/5/13 and dating scan said 14/5/13... So mine was a pretty close range... Scans are pretty good as they check measurements of baby and work the weeks and that out from that... I'd go by what the hospital are saying instead of stressing yourself out xx

bebemoose Sun 11-Nov-12 22:40:23

Hi confused - if you have had two scans at 9 and 12 weeks giving you a due date only two days different then it should be pretty accurate. We usually quote scan dates as plus or minus 5 days at 12 weeks. So with your due date of 20th February you should have conceived around the 30th May, give or take 5 days. You definitely didnt conceive in April with those dates, so you can be reassured that the friend is not the father!

It sounds like your actual last period was at the end of April and you conceived late in the cycle (which is perfectly possible as ovulation is not always on day 14). Hope this helps.

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