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 membrances
  • 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 ref

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

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Article information

rID: 15495
System: Obstetrics
Tag: cases
Synonyms or Alternate Spellings:
  • Cephalic index (CI)

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