Ultrasonic Fetal Biometry in Jos, Nigeria

Abstract

Fetal biometry has been studied using large sample sizes in the developed countries and reference values created for their population but the sample sizes that have been used in Nigerian studies are very small to provide statistically significant data for the relationship between gestational age and fetal parameters. The purpose of this study was to find out the mean values of biparietal diameter, head circumference, occipitofrontal diameter, abdominal circumference, femur length and weight of fetuses in Jos from 12 weeks to 42 weeks of gestation and also to determine the relationship of the aforementioned fetal parameters to gestational age and symphysio-fundal height. Reference values for fetal biometric parameters are important because the study of normal and abnormal growth of fetuses has become an increasingly important part of the practice and research in all fields related to child health. In a cross-sectional study conducted on 13,740 Nigerian fetuses in Jos ranging from 12 weeks to 42 weeks at the Centre for Reproductive Health Research Jos; fetal biometric parameters were measured using ultrasound machine and mean values determined after analyzing the data statistically. The relationship between the derived mean values of the various fetal biometric parameters and gestational age were studied. Mathematical modeling of data demonstrated that the best-fitted regression model to describe the relationship between biparietal diameter and gestational age is a positive polynomial correlation with a correlation of determination of R2 = 0.9996 (P < 0.0001) in Nigerian fetuses in Jos. The relationship is best described by the second order polynomial regression equation y = – 0.0511x2 + 5.3221x – 35.511 where y is the biparietal diameter in millimeters and x is the gestational age in weeks. A similar correlation was found between gestational age and occipitofrontal diameter with a correlation of determination of R2 = 0.9996 (P < 0.0001) which is described by the third order polynomial regression equation y = – 0.001x3 + 0.0137x2 + 4.671x – 27.99 where y is the occipitofrontal diameter in millimeters and x is the gestational age in weeks. Again, a positive polynomial correlation between gestational age and abdominal circumference with a correlation of determination of R2 = 0.9995 (P < 0.0001) was found in Nigerian fetuses in Jos. The relationship is best described by the fourth order polynomial regression equation y = – 0.0004x4 +0.0349x3 – 1.2485x2 + 30.598x – 172.02 where y is the abdominal circumference in millimeters and x is the gestational age in weeks. Furthermore, mathematical modeling of data demonstrated that the bestfitted regression model to describe the relationship between femur length and gestational age was the second order polynomial regression equation y = – 0.017x2 + 3.2794x – 25.282 with a correlation of determination of R2 = 0.999 (P < 0.0001) where y is the femur length in millimeters and x is the gestational age in weeks. Mathematical modeling of data demonstrated that the bestfitted regression model to describe the relationship between weight and gestational age was the power regression equation y = 0.038x3 where y is the fetal weight in grams and x is the fetal age in weeks with a correlation of determination of R2 = 0.9951 (P< 0.0001) in Nigerian fetuses in Jos. When fetal weight was plotted against symphysio-fundal height, it was found out that there is a positive correlation between fetal weight and symphysio-fundal height with a correlation of determination of R2 = 0.9951 (P< 0.0001) in Nigerian fetuses in Jos. The relationship is best described by the power regression equation y = 0.0409x3 where y is the fetal weight in grams and x is the symphysio-fundal height in centimeters. Growth of the fetal biometric parameters in the study population showed a curve similar to that of Europeans. The study identified a 19th week gestation problem (characterized by decrease in growth rate of fetal parameters measured with concomitant weight loss) which will require to be pursued by future investigators. It is concluded that biometric parameters in Nigerian fetuses in Jos correlated well with gestational age and symphysio-fundal height.