Please or to access all these features

Add post

Watch this thread

Save thread

Start a new thread

Flip thread

Hide thread

My feed

Active Unanswered threads

Getting started FAQ's

Unanswered threads Acronyms Talk guidelines

Hide shortcut buttons

Talk

Conception

When's the best time to get pregnant? Use our interactive ovulation calculator to work out when you're most fertile and most likely to conceive.

Flip

Original poster

Confused with due date/conception date?

15 replies

yasfci · 27/01/2017 11:36

I'm currently 13 weeks 3 days pregnant and this date is going by what the sonographer told me on Monday with due date of 1st August.
However i'm a bit confused, I was on the contraceptive pill when i fell pregnant and my LMP was on the 8th October. Working out dates i should be 15 weeks + 6 days...
Is there any chance that the sonographer's arn't always 100% with dates? My bump also feels a lot bigger to what i thought a normal 13 week bump would look.
Has anyone had an incorrect date for due date ?

OP posts:

ShowOfHands · 27/01/2017 11:43

Are you trying to work it out based on your LMP? Your last period is irrelevant, pregnancy is dated from conception. Two women can have a last menstrual period on the same day and one ovulate on day 10 of her cycle and the other ovulate on day 31. They have the same LMP but will have a due date difference of 3 weeks.

Your scan suggests you conceived somewhere around the first week/10 days of November.

There is a margin for error but it's only a few days either way.

Spam88 · 27/01/2017 15:56

I don't think periods when you're on the pill can actually be used to date your pregnancy, as they're not actually periods. Regardless, the date from your scan is more accurate.

SofiePendragon · 27/01/2017 20:26

The sonographer could have made an error with the measurement, or you may have conceived later than you thought. When did you first have a positive pregnancy test?

TurquoiseDress · 27/01/2017 23:28

I think the dating scan around 12-13 weeks is one of the most accurate times to date a pregnancy.

Last period tends to be irrelevant as it depends on how long your cycles are i.e. when you ovulate, is it early or late in the cycle.

Often, looking at the dates when you had sex don't help either- it could be a few days later that you ovulated and conceived.

With being on the pill that wouldn't have been a real period i.e. the cycles were controlled by hormones and not your actual menstrual cycle

MoonlightMojitos · 28/01/2017 00:06

The dating scan can still be quite far out IMO. They moved me forward 8 days even though I 100% know conception date. The date they gave me meant conception when AF was still here and I know it's wrong. Had my 20 week scan a few weeks ago and all the measurements are slightly on the small side so actually about right for 19 weeks not 20... I think either my dating scan measurements were wrong or baby had a growth spurt just before and has now gone back to where he should be for dates.

As others have said though being on the pill will have messed with your cycle and I'd go by those dates as will be more accurate than lmp.

jade1245 · 27/02/2017 14:00

hi I am 10 weeks pregnant and I am so stressed out this is my second pregnancy I had really bad postnatal depression with my 1st and so worried it's coming back again. so I had a scan on the 2nd Feb which put me at 6 weeks 4-3 days and then I had another on the 22nd Feb which put me at 9 weeks 1 day i need to know how accurate these scans are as I don't remember my LMP date I've tired to rack my brains but I just csnt figure it me n my bf broke up.n I had sex with someone on the 21st of Dec and me n my bf got bk together the next day I had sex with him around Xmas time my doctor says it's fine I would of completely missed it with the other person as by the scan I would of fell pregnant beginning of Jan and sperm can only live up to 3 to 5e days inside you. but I just can't shake this feeling I feel like I'm going insane I've been reading up on it every single day my head feels like it's going to explode I just csnt deal with it anymore someone please help I'm so scared because of what I done n I'm an over thinker I'll go back into a deep depression

Starfish83 · 27/02/2017 14:03

Jade, I am sorry for what you are going through, but you need need to start your own thread as your post is not relevant to this one. Begin your own thread and people will be able to share advice appropriately.

jade1245 · 27/02/2017 14:26

is this thread not talking about the accuracy of scan dates maybe I shouldn't share so much information as I'm getting shut down left right and centre on this site. I thought this site was for advice clearly not!!

Starfish83 · 27/02/2017 15:58

Not at all, Jade. My post was trying to help you to get your post seen. Due to the nature of your issue, I was rather concerned about you and, therefore, thought it probably best to start your own thread so that people will prioritise your message as it will be the first post. I hope that make sense.

jade1245 · 27/02/2017 16:23

yeah sorry it's just had a rude person keep commenting everywhere I was posting this I took ur advice and started my own thread n have had loads of replies sorry again just so very stressed about everything x

Starfish83 · 27/02/2017 18:41

Thanks, Jade. Really hope that you get some support, and that you have a healthy pregnancy. Take care.

WantToGoingTo · 02/03/2017 16:59

Hi Jade from looking at your dates I would say with either scan it would be impossible for the other man to be the father if you had sex on 23 December. Likelihood is baby was conceived sometime around new year/early January (estimated ovulation at day 14 puts it at either 2 or 3 Jan based on those scan dates). 23 December would have been only just after af so not likely at all. Can completely understand how horribly nerve wracking that would be for you though as I assume your boyfriend doesn't know?

WantToGoingTo · 02/03/2017 17:02

Op - 12 weeks scans are most accurate at dating. Any dating done at 20 weeks isn't as accurate. However, I knew when I had ovulated when I was pg as I used opk and scan measurement put my date forward 6 days so I protested and they let me keep my original date :D I gave birth at 39+4 by my dates so I think mine were more accurate! As you don't know lmp cos of the pill I would go with scan date. You may have lots of waters or a big baby!

WantToGoingTo · 02/03/2017 17:02

Or indeed good old first trimester bloating... :)

CR1412 · 30/04/2019 15:50

Help. I’m currently 13 weeks 6days. I had a scan at 11 weeks 2 days with a due date of 30th October . At that time I thought I was only around 8/9 weeks. I split with my partner and I had sex with my 1st child’s dad on 6th February. My LMP was around 21st January but I’m not 100% sure and it was only a 3 day period. I had sex with my current partner everyday on the weekend of 25th January. The person that did my scan says I was too far gone for my 1st child’s dad to be the father (the person I had sex with on the 6th February) But when I work out my conception date it comes up with dates from 4th feb to 8th feb. I so confused and scared I really don’t know what to do.

Flip