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What is FL in pregnancy?

Published in Fetal Development 1 min read

FL in pregnancy stands for femur length, which is the length of the femur bone in the developing fetus. This measurement is a key indicator of fetal growth, especially after the first trimester.

Understanding Fetal Measurements

During pregnancy, ultrasound measurements help assess the baby's development. While CRL (crown-rump length) is more accurate in the first trimester, other parameters like FL become more useful after 12 weeks.

How FL is Used

  • Estimating Gestational Age: Femur length helps determine how far along the pregnancy is.
  • Assessing Fetal Growth: By comparing FL to standard growth charts, doctors can identify potential growth abnormalities.
  • Detecting Skeletal Dysplasia: Significant deviations in FL can be an early sign of certain skeletal conditions.

Other Important Measurements

While FL is important, it's often considered alongside other measurements:

Measurement Description Timing
CRL Length from the top of the head to the bottom (crown-rump) First Trimester
BPD Biparietal Diameter (head width) Second/Third Trimester
HC Head Circumference Second/Third Trimester
AC Abdominal Circumference Second/Third Trimester
FL Femur Length (length of the thigh bone) Second/Third Trimester