How accurate is the date from my scan?

[Jess721]

I had my first scan yesterday and was told I'm 14 weeks 1 day pregnant. I was confident I was 11 weeks and 3 days. The dates are quite crucial, if I'm 14 weeks, it's my ex's! How accurate is the dating?

[roxannacar]

It's operator dependant but fairly reliable. However I would never be happy assuming paternity on a scan, but you need to a DNA test.

[Jess721 in reply to roxannacar]

Thank you. I see some very awkward conversations ahead!

[SilkeP]

As previous comment..

But also, my 6 week scan was wrong by a week in my opinion and was told that's impossible, I was sure as i knew exactly when my ovulation was... At my 12 week scan it turned out the earlier scan HAD been wrong by a week.

However, for it to be wrong by 3 weeks at that stage I would say is impossible. 3 weeks is a long time and the baby at 11 weeks compared to 14 weeks is a LOT smaller.

But yes, you'd need a DNA test to be 100% sure.

[Jess721 in reply to SilkeP]

Thank you. I'm going to spend some more quality time with a calendar, but I see this being a bit difficult!

[SiameseCatLady]

You can measure oddly in scans but usually only up to 12 weeks I heard. Mind you I am 39 weeks and my baby is measuring 40+ weeks in some parts of body so all weird.

Think about your periods as well...

Can it really be one of two people's if it's a 3 weeks gap? You would have 'timed it perfectly' if so.

Check it out with period dates before you tell your current partner/ex partner.

[Katie14]

I haven't had a scan yet so i'm not sure whether the date will change or no. At the minute the doctor is saying 5 weeks 5 days which is taken from the first day of my last period. As my partner was away for 2 weeks at that time i know i'm only 3 weeks and 2/3 days.

[Jess721]

I have managed to establish that how many weeks pregnant you are is the date of conception plus 2 weeks. This accounts for the difference plus an acceptable margin of error, and explains why they counted from before I had sex! Would have been very helpful if this had been explained at the scan!

[roxannacar in reply to Jess721]

The midwife, gp, scan date etc are always calculated from the last period and never from the date of conception.