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Original poster

Scan dates

4 replies

Cancun26 · 05/02/2025 11:04

Morning mumsnet. I’ve just had my 12 weeks scan and the foetal was in position where couldn’t get accurate measurements. I know when I had sexual intercourse is it normal for the scan dates to be out 2-5 days? For instance I should be 12 + 2 days from my conception date and they’ve put me at 12 + 5 days from LMP? X

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sel2223 · 05/02/2025 11:32

Yes this can be normal, they tend to work with LMP unless measurements say otherwise.

Also bear in mind that sperm can live inside of you for 5 days so even if you know the date you had intercourse, it may have been up to 5 days later that you actually ovulated

JuneySunshine · 05/02/2025 11:32

Hello,
Yes ofcourse its normal for them to be out. They work on the basis of everyone having a 28 day cycle just so they can decide when to send you for the first scan.
With both my pregnancies my cycle has been 35 days, so I ovulate 7 days later than their system predicts, so they send me for a scan a week earlier than they 'should'. Once they can get some proper measurements that will firm up your actual gestation period and due date. It may or may not be exactly what you think due to the possibility the sperm and egg didn't meet immediately i.e. on the conception date you have in mind.

Original poster
Cancun26 · 05/02/2025 11:39

JuneySunshine · 05/02/2025 11:32

Hello,
Yes ofcourse its normal for them to be out. They work on the basis of everyone having a 28 day cycle just so they can decide when to send you for the first scan.
With both my pregnancies my cycle has been 35 days, so I ovulate 7 days later than their system predicts, so they send me for a scan a week earlier than they 'should'. Once they can get some proper measurements that will firm up your actual gestation period and due date. It may or may not be exactly what you think due to the possibility the sperm and egg didn't meet immediately i.e. on the conception date you have in mind.

Oh I see I have had 33 day cycle so should have ovulated around day 20 of my cycle but I only had sex day 17 on my cycle x

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Original poster
Cancun26 · 05/02/2025 11:40

sel2223 · 05/02/2025 11:32

Yes this can be normal, they tend to work with LMP unless measurements say otherwise.

Also bear in mind that sperm can live inside of you for 5 days so even if you know the date you had intercourse, it may have been up to 5 days later that you actually ovulated

ah I see that’s good to know.‘thank you x

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