Cephalic index: A gestational age-dependent biometric parameter

Diana L. Gray, Giuliana S. Songster, Curtis A. Parvin, James P. Crane

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Cephalic index was proposed originally as a means of recognizing altered head shape and confirming the validity of biparietal diameter (BPD) measurements. Two previous studies found cephalic index to be gestational age-independent. We tested this relationship by regression analysis in 777 well-dated pregnancies, evenly distributed between 14–40 weeks’ gestation. Significant variation in cephalic index was found with advancing gestational age, with the highest and lowest values observed at 14 and 28 weeks, respectively. Based upon application in a separate test population of 1361 normal fetuses, a threshold of ± 1 SD maximized identification of misleading BPDs due to altered head shape.

Original languageEnglish
Pages (from-to)600-603
Number of pages4
JournalObstetrics and gynecology
Issue number4
StatePublished - Oct 1989


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