<prompt> All of the following are commonly used for estimation of gestational age in mid trimester EXCEPT: March 2013Biparietal diameterCrown Rump LengthAbdominal circumference of fetusFemur length  <response>: Ans. B i.e. Crown Rump Length CRL is most accurate with an error of 2.1 days in the first trimester BPD, FL, HC head circumference AC is commonly used for dating thereafter. 