Author(s): Nagesh R1, Anil Kumar Shukla2, Seetha Pramila V. V3

Cephalic index is the ratio of head’s breadth to length, which reflects the cranial dimensions and is an important parameter in anthropometry. Cephalic index is also known as cranial index and was defined by Swedish professor of anatomy Anders Retzius. It is useful to differentiate different types of crania belonging to different races, gender, age, geographical zones, tradition and nutrition, etc.
To estimate foetal cephalic index by ultrasonography, to classify foetal heads as per international categories and to know the frequent head types in second and third trimesters of pregnancy.
This prospective cross-sectional study included 100 normal singleton pregnant women with foetuses in the duration 12 to 40 weeks of gestational age. By ultrasonography, foetal head breadth and length was measured. Cephalic index was calculated by Breadth/Length X 100 and all the heads were classified as per international categories.
Of the total 100 foetal heads in the gestational age of 12 to 40 weeks, the mean cephalic index was 78.95±03.01. Mean biparietal diameter was 68.04±22.26. Mean occipitofrontal diameter was 86.38±28.61. According to cephalic index value 51% mesocephalic, 38% brachycephalic, 10% dolichocephalic and 1% hyperbrachycephalic heads were noticed. A mean cephalic index of 80 at 12-16 weeks, 78.48 at 36-40 weeks and a constant cephalic index of 78 to 79 was observed between 16-36 weeks.
The mean cephalic index in the present study was 78.95 and is of mesocephalic phenotype in our study. It is the most frequent head type noticed. A linear correlation was observed between gestational age versus biparietal diameter and occipitofrontal diameter. No linear relationship was seen between gestational age and cephalic index. Brachycephalic heads at 12-16 weeks, mesocephalic heads at 36-40 weeks and a constant cephalic index of 78 to 79 was noticed from 16 to 36 weeks of gestation.

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