What is the most a fetal dating scan can be wrong

[cherry6]

Hi everyone, I have been wondering at most how much a scan can be wrong. I found out quite late that I was having a baby (16 weeks) and am now 26 weeks according to a dating scan at 18 weeks. I have had an anomaly scan at 20 weeks all seems well. My question is probably completely irrational, but the mind can play tricks, can a scan at 18 or twenty weeks be 10 weeks out, my husband and I have split up ( i would have been about 12 weeks when he left if scan is correct) and about 11ish weeks after he left I had a regrettable one night stand. I will probably be bringing baby up alone, but would still like it to be my husbands. Am I just being an emotional baby brain, or could I only really be around 13 weeks pregnant not 26 :)

[Febbaby272]

Hi just wondering can anyone help with dating scans I hate mine at 11 weeks and 3 days it measured 48 mm my lmp was 11th may so they say I conceived round day 11 I usually have 42 day cycle which would of left me fertile round June 8th could it be wring by two weeks or might o just ovulated early has this happened any one else ??

[cherry6]

Thank you for the reply, I know i'm being irrational but its nice to hear someone elses thoughts as I don't really have anyone I can talk to about this :)

[AnnieBrooke]

By the time the baby is full term, an ultrasound date (in relation to the date of conception) might possibly be two weeks off, but not ten.  A scan at 18 weeks wouldn't even be so far off as that.  A week at most, maybe even only five or six days.  :)

[cherry6]

Thanks for that :) I was kinda hoping someone would tell me how ridiculous I was being, 10+ weeks out sounds so silly when I say it out loud lol

[ku111]

The earlier a scan is done the more accurate the date.  Ask your dr.  Wishing you the best!  Congrats!