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Can 12 week dating scan wrong

And yet, bizarrely, after your dating scan at 12 weeks, your due date can get accurate the more pregnant you get.Sonographer Jan Steward explains, “As your baby gets bigger all of the usual differentials start to happen between big and small babies so it’s much harder to be accurate.

The healthcare professionals will stick to this date as far as possible because it is then used as the baseline for growth throughout pregnancy." While the professionals like to try and stick with the date that you’re given at your dating scan, it can and does change. "I'm 16 5 and have already been given 3 due dates and its changed for a 4th time back to the 2nd estimated due date! I have scans every few weeks so it will probably keep on changing.There would be so many variables if it was calculated from when you 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. This is especially true if you have an irregular cycle or have been on the Pill for example.“All the dates I was given were wrong up until my 12 week scan - which gave my EDD as one day before the date I had calculated myself!” Expert Jan Steward, who is director of Ultrasound Direct and Babybond, agrees that early scans carry a much greater risk of inaccuracy.“Definitely agree that dates from early scans are not accurate.

Just half a millimetre at such an early stage can change your date by a week. "I fell over at ‘7’ weeks by my last menstrual period (EDD 18 March) and was sent for an early scan.

“I was measured at 6 6 (6 weeks and 6 days) when I should have been 8 weeks.

Measurements at such an early stage aren't accurate which is why they wait for 12 weeks to date you.

The sonographer then said that I was only about 4.5 weeks [EDD 2 April].

Then at the 12-week scan I got an EDD of 15 march, so that early scan was completely out.

Had a pregnancy ultrasound that doesn't match your Estimated Due Date (EDD)?