Cephalic Index: A Fetal Gestational Age Dependent Biometric Parameter

Abstract

Objective: There is limited data on fetal cranial dimensions of Nigerian population. This is important because the study of normal and abnormal growth of children has become an increasingly important part of the practice and research in all fields related to child health; more so that prenatal and postnatal growth is one continuous process. Material & Methods: In a cross-sectional study conducted on 13,740 Nigerian fetuses ranging from 12 weeks to 42 weeks at the Centre for Reproductive Health Research Jos; biparietal diameter and occipitofrontal diameter were measured using ultrasound machine in order to calculate fetal cephalic index. The values were statistically analyzed after deriving the relevant indices. Results: The regression equation was calculated between gestational age and cephalic index of fetuses of Nigerian women. This equation y = 1.3x + 59.88; showed a linear relationship which was stronger from 12 to 16 weeks of gestation. Above 16 weeks gestation, the relationship was found to be quite weak. Coefficient of correlation is r2 = 0.9844 (p < 0.0001). Conclusion: The fetal skulls were found to be mesocephalic in the early weeks and brachycephalic at term.

Keywords

• cranial dimensions
• cephalic index