cephalic index

The cephalic index (CI) is a value calculated using two fetal biometric parameters which are the occipitofrontal diameter (OFD) and the biparietal diameter (BPD).

It is calculated as:

  • cephalic index (CI) biparietal diameter (BPD)/occipitofrontal diameter (OFD)  x 100 

The cephalic index gives an idea of the fetal head shape. It can change according to various situations such as

  • presentation, e.g. breech presentation
  • ruptured membranes
  • presence of a twin pregnancy

The usual range is variable depending on various sources and different demographic groups. Often the mean value is taken ~78 (range 74-83 )

A grossly decreased cephalic index suggests dolichocephaly while a grossly increased one can suggest brachycephaly.

Siehe auch: