Accuracy of crown-to-rump length

kmp2kmb

Does the accuracy of the CRL decrease the further into the pregnancy you go.  We had an u/s yesterday at 15w5d and up until this point they were all within a day or two and this one said 14w6d which wasn't that far off, but everything else seemed fine and the doctor didn't comment.  The only reason he measured was b/c DH asked how long the baby was.  I had read that its usually used in weeks 5-12 to date the pregnancy for the due date, but after that I don't know how much they use it after this time. 

MrsL.inMarch

Human error is always a factor. And they will always measure during an ultrasound, that is what they are for (unless it's to check fetal heart tones or something).

I'm not sure what your real question is though. Can meausurements be off? yes. Can the baby measure ahead or behind the standard? yes.