SONOGRAPHIC ASSESSMENT OF FETAL CEPHALIC INDEX AMONG KANURI POPULATION IN NORTHERN NIGERIA

BACKGROUND: The cephalic index, which is the ratio of the biparietal diameter to the occipitofrontal diameter, is a key metric for classifying fetal head shape. Its normative values are population-specific, and data on the Kanuri ethnic group of Northern Nigeria are lacking. Establishing population-specific reference data is crucial for accurate gestational age estimation and early detection of cranial anomalies. AIM: This study aimed to establish a nomogram of the fetal cephalic index of the Kanuri population and derive a regression-based correction equation for adjusting atypical head shapes to improve the accuracy of gestational age dating. METHODS: A prospective cross-sectional study was conducted involving 389 healthy singleton Kanuri pregnancies at Maryam Abatcha Women and Children Hospital, Maiduguri, Nigeria. Standardized transabdominal ultrasonography was performed to measure the biparietal and occipitofrontal diameters. The cephalic index was calculated as (biparietal diameter occipitofrontal diameter) × 100. Statistical analyses included descriptive statistics, Pearson’s correlation, and regression modeling to develop a correction equation for biparietal diameter. RESULTS: The mean cephalic index was 77.89 (±4.44), range: 65.16–101.27, classifying the population as predominantly mesocephalic. The cephalic index showed weak but significant positive correlations with gestational age (r=0.116, p=0.022), biparietal diameter (r=0.120, p=0.018), and femur length (r=0.124, p=0.014). A significant difference was found between the cephalic indices of the foetuses in the cephalic and breech presentations (78.30 vs. 76.35, p<0.001). Comparative analysis revealed significant differences from the Igbo (p<0.001) and Fulani (p<0.001) populations, but not from the Yoruba pose findings underscore the necessity of population-specific biometric standards in prenatal care.