title: Cephalic index: a gestational age-dependent biometric parameter.
abstract: 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.
authors.affiliation: Department of Obstetrics and Gynecology, Washington University School of Medicine, Jewish Hospital of St. Louis, Missouri.
authors.forename: D L
authors.initials: DL
authors.lastname: Gray
authors.forename: G S
authors.initials: GS
authors.lastname: Songster
authors.forename: C A
authors.initials: CA
authors.lastname: Parvin
authors.forename: J P
authors.initials: JP
authors.lastname: Crane
mesh_terms: D002508:Cephalometry; D005260:Female; D005323:Fetal Monitoring; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D012016:Reference Values; D014463:Ultrasonography