Instructions Biometry Calculator

INSTRUCTIONS FOR THE FETAL BIOMETRY CALCULATOR
This form will calculate the percentile for a fetal measurement at a given gestational age (EGA) based on published reference tables.

1. Enter the best gestational age of the fetus in weeks.
2. Enter the measurement (mm or grams) you obtained on ultrasound.

3. Press the button for the parameter you are measuring such as the femur length.

If there is no value for the measurement at the gestational age you entered you will be told the range of ages the calculator does have values for.

4. The form will calculate the percentile of your measurement for the gestational age you entered.

Example: We are evaluating the femur length at 32 weeks and we measured it as 63 mm.

1. EGA (weeks) = 32
2. measurement (mm) = 63

3. Press Femur

The calculator should read 79 percentile.
Which means the femur length 63 mm is the 79th pecentile for a fetus at 32 weeks based on the cited reference for the femur length.
The process is similar to looking the value up in a table.