why would sonographer need to consult their chart on size measurement

[piklepants]

I'm early stage pregnant had scan and woman needed to consult chart to work out size dates why would this be? Surely they scan all time or was it because I'm earlier on than she's used to scanning? She was an experienced sonographer?

[hazchem]

I wouldn't worry. Double checking is good. Like when a GP checks that the amount they are prescribing is right or the advice is up to date in the little book thing.

[Roshbegosh]

You think she should memorise the normal size and all centiles for every day of the pregnancy? Of course she checks against charts or else the machine does it. Nothing to worry about.

[PastaandCheese]

As rosh says expected size of various structures changes everyday in early pregnancy so she can't be expected to remember.