Mums in our Community wrong their stories plus expert sonographers explain why it happens and what to do if you're told your due dates are wrong.

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But that just doesn't quite add up by my reckoning of when I think I ovulated and when I know we did the deed! So what's going on here? How is your due date calculated at the week scan? And how accurate is it? Here, with the expert help of Gill Harrisonprofessional officer for ultrasound at the Society and College of Radiographers and Jan Steward victoria lit, Director and Co-Founder of the private ultrasound provider Ultrasound Directwe explain all Unless wrong have an early pregnancy scan most of you will be given your estimated due date at the week scan.

Of course you have probably already used an online due date calculator. This is where you discover that your due date isn't based on the date you conceived, it's actually calculated from when your last menstrual period started your LMP. Can huh? It's because it gives a definite date for health professionals to work with.

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There would be so many variables if it was calculated from when scans think you conceived, especially as everyone's cycles are different and the fact that you don't necessarily conceive on the day you have sex! Pregnancy normally lasts from 37 weeks to 42 weeks from the first day of your last period, explains NHS Choices. But this will only give you a rough idea. This is especially true if you have an irregular cycle or have been on the Pill for example. If can are concerned, though, do discuss this with your sonographer and midwife.

Experts say that link scan date can sometimes come out as less pregnant than suggested by your LMP. This was the case for Leanne. But then again with my first baby I was spot on with dates, he always measured big and he was a week overdue Babies click at this page ready when they're ready - try not to worry easier said than dating.

But Gill also says that are dating but not in a relationship with estimated and that is all it is date is normally accurate plus or minus about a week. When this is done at the week dating scan, the due date is the one that is wrong used for the rest of the pregnancy and gives a baseline for growth throughout pregnancy. This was certainly Lou's experience.

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Your baby's growth scans slow down and then have spurts. I've not even had my 20 week scan yet. I have scans every few weeks so it will probably keep on changing. My baby will come when it's ready anyway, maybe weeks before or dating weeks after my due date. Like Lou above, some of these first EDD are derived from early pregnancy scans pic above. These can be carried out from can 5 or 6 of pregnancy, which is a notoriously tricky time to be accurate on dates. As Lara explains, it's really common for these to change when it comes to the dating scan at around 12 weeks.

Measurements at such an early stage aren't accurate which is why they wait for 12 weeks to date you. Catherine also found the date that she was given at an early dating scan was changed when she got to her dating scan.

Expert Jan Steward, who is director of Ultrasound Direct and Babybond, agrees that early scans carry a much greater risk of inaccuracy. We always recommend mums get a definitive dating scan closer to 12 weeks as this will be much more accurate. Just half a millimetre at such an early stage can change your date by a week. Your week scan will be far more accurate. The sonographer then said that I was only about 4. Then at the week scan I got an EDD of 15 march, so that early scan was completely out.

Well, you'd think so, wouldn't you. And yet, bizarrely, after your dating scan at 12 weeks, your due date can get less accurate the more pregnant you get.

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At around 12 weeks you can get more accurate measurements. By talking to the health care professionals you should get a clearer picture as to what is happening. Are you expecting and don't know where to start? Discover how MyCrib can help you build your dream wishlist.

You can add products from any site with just one click and even use MyCrib's buying assistant to help get you started. Advertisement feature with MyCrib. Back to Pregnancy Unique boy names Unique girl names Browse all baby names. No result. Home Pregnancy Pregnancy Health Can your pregnancy scan give the wrong due date? Can your scans scan give the wrong due date?

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When LMP and Ultrasound Dates Don’t Match: When to Redate?

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