Can I tell you of my experiences?
DS was born 3 days early from lmp edd.
DD's lmp, knowing that we were ttc and always marking calendar when AF arrives as matter of course, was 27/05. Scan at 12 weeks changed it to 18/05 - 9 days! Considering I have a 24 day cycle that means I'm supposed to have conceived on day 2 of AF... WTF! I digress, sorry.
Anyway, they ignore our protestations of dates, afterall we weren't there at conception, were we?
I allow myself to work to 18/05 and even assume dd will be early because of ds being 3 days early (probably caused by falling and suffering a greenstick fracture in wrist 7 days previously, therefore shock to system).
When we get to 41wks scan I am fighting them off, they want to induce and on a scarred uterus too!
I continue to fight them off and have two unsuccessful sweeps at 41 and 41+5 scan. Cervix no where near ready!
Cancel induction booked for 42wks scan and bargain for more time using MY LMP dates. Agree to daily Expectant Management thereafter, agree to another sweep in desperation for VBAC and it is successful, a, 2cm, thinning etc, Bishop's Score of 8.
Deliver dd next day. 42+1 scan or 40+6 lmp
Cutting long story short: scans for dating and sizing are notoriously inaccurate! Trust yourself, especially if you know your cycle and when you had sex!
Also with hindsight I won't bother having sweeps in future, as they can cause infection, can accidently break waters, can demoralise if unsuccessful and don't actually tell you anything except what your cervix is doing at that exact time and at best will indicate that labour may be immininet but not when.
So that's my experience and my opinions!
I suggest you enjoy the twilight of your pg and the special bond you alone share with baby before it is born.
Sending happy, calm labour vibes to the ladies in waiting!