Comment by gdh73

I was wondering the same since the Crown–rump length (CRL) measurement only has two points. One would think the spine should be included for an accurate measurement. However, that must be accounted for already. See also, "3. First-trimester fetal measurements" and "4. Assessment of gestational age" here: http://onlinelibrary.wiley.com/doi/10.1002/uog.12342/full