Table 2.
| Fetal-Pelvic Index | |
| Combines 4 measurements of the fetal head circumference and abdominal circumference with the maternal pelvic inlet and outlet measurements. | |
| The sum of the two most positive fetal-pelvic circumference differences | |
| A positive FPI should identify fetuses larger than the maternal pelvis | |
| A negative FPI should identify fetuses smaller than the maternal pelvis | |
| Calculation: HC-IC, HC-MC, AC-IC, AC-MC | |
| Cephalopelvic Disproportion Index | |
| The smallest pelvic diameter (either the anteroposterior of the inlet or the bispinal of the midpelvis) compared to the biparietal diameter of the fetal head | |
| The difference between the two indicates how much wider the smallest diameter of the bony pelvis is than the fetal skull | |
| A positive index is present if the pelvic diameter is less than 9 mm wider than the biparietal diameter. |
HC Head circumference, AC Abdominal circumference, IC Pelvic inlet circumference, MC Mid-cavity circumference