Parameters used to estimate gestational age in last trimester – a) CR lengthb) Abdominal circumferencec) BPDd) Femur length
Estimation of age by USG

1st trimester :- Crown - rump length (CRL).
2nd trimester :- Femoral length (FL), Biparietal diameter (BPD)
3rd trimester :- Femoral length, Biparietal diameter, abdominal circumference (AC), head circumference (HC).
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