Can a dating scan be out by a month ?

[Keyvalyons]

Just a few questions about my first scan ... I am now a few days over 20 weeks ! When I went for my first scan I was told I was 16 weeks ! I had sex 2 weeks before my period and also two weeks after my period ! I took the morning after pill after the two weeks before my period and my period arrived on time but only lasted two days I presumed that was because I took the morning after pill ! When I went for my scan I was told I was 16 weeks and also this matched my Lmp which I'm presuming would mean I was 14 weeks so this would mean I got pregnant the 2 weeks after my period ! Just wondering would this be accurate or could the dating scan be off my a month ?

[Mosaic]

From my own experience with my second child, not only can conception be very unexpected and deviously hidden - even if you think you know your own body - but also, the way baby's growth is measured and predicted is based on averages and individual babies can grow more quickly or a bit more slowly. Provided there are no other bad signs such as high blood pressure in the mother this doesn't really matter. In all, there was a full four weeks between the first due date I was given and his eventual decision to appear.

[sedum21]

Normally dating scans are very accurate, in fact I've never heard of one being wrong at all. Not sure if this is good or bad news for you - I hope good x

[NOX]

Our one chiuld was a full three weeks late and another 2 weeks early from their official dates- just depends if your baby is small or large for dates. As mosaic said it's all based on averages.

[Traci66]

My first was born three weeks before the due date given by the scan and my second five weeks before, the second weighed six pounds at birth.

[Hafsoh]

Dating scan are usually accurate but can be a week or so out, ovulation may not always be accurate though it does depend on many factors along is how big your baby is etc.. Ovulation occurs 12 to 16 days before the menstrual period begins and conception could happen 3 to 6 days after ovulation.

scan are usually accurate but of course not 100% there is always a small margin for error.