Determining Due Date: BPD vs. Femur Length - What's Used?

The femur length is not used to determine the due date. BPD (biparietal diameter) is the measurement of the widest part of the baby's head from one side to the other. It is used along with other measurements, such as head circumference, abdominal circumference, and the length of the long bones, to estimate the gestational age of the fetus and to determine the due date.