Sonographic Assessment of the Fetal Heart Circumference as a Predictor of the Gestational Age

Introduction: Ultrasound is a non-invasive imaging modality, safe for both the mother and the fetus, which uses a high frequency sound to generate images of body tissues and organs. It has been widely used for fetal evaluation and dating. Purpose: To determine normative values of fetal heart circumference (FHC) as a predictor of the gestational age (GA) in black population and compare it to those of the Caucasian population. Material and Methods: A prospective cross-sectional study was carried at the University of Maiduguri Teaching Hospital (UMTH), Nigeria. 324 women with a singleton pregnancy between 12-40 weeks, who conceived naturally, were scanned using a 2D ultrasound machine with a 3.5 MHz curvilinear probe. Two fetal heart diametersat right angle to each other were taken at the level of the four-heart chamber view, during diastole. Results: There is a strong positive linear correlation between the FHC and the GA (r2= 0.964, p<0.001). The equation of GA prediction is Y=0.246X + 5.06 (where y=GA, X=FHC). FHC weekly growth rate is 3.81mm. FHC is more accurate between 12-20 weeks GA and its accuracy decreases as the pregnancy progresses. There is a strong correlation between FHC and biparietal diameter (BPD) (r2=0.959), HC(r2=0.946) and FL (r2= 0.962). Conclusion: The study has derived a nomogram of FHC as a predictor of the GA in Nigerian population and has shown that the FHC is a good predictor of GA especially in the early second trimester. Also, there was a statistically significant difference between the FHC in our study population (blacks) and those of the Caucasian population.