The Prediction of Fetal Maturity and Gestational Age by Ultrasonic Measurement of Distal Femoral Epiphyseal Secondary Ossification Center

Abstract

Objective: The aim of this study was to determine the diameters of the distal femoral epiphyseal secondary ossification center (DFOC) in the
various gestational ages (GAs) as well as to create a novel equation, through which GA can be calculated from the measurement of DFOC.

Materials and Methods: EDAN Digital ultrasonic diagnostic imaging system (model DUS 3 made by EDAN, Korea) and a 3.5MHz Convex transducer were used for the sonographic measurement. Ultrasonographic examinations were performed on 999 normal singleton pregnancies with GAs ranging from the 28th to the 41st weeks. Patients were recruited from the University of Calabar Teaching Hospital to Assurance Medical Diagnostic Center, where the ultrasonographic examinations were carried out. Images of the long axis of the fetal femur were taken. The DFOC was visualized as a small echogenic, ovoid structure lying adjacent to the distal femur. Three measurements of the DFOC diameter (in mm) were taken from outer to outer margins, and the largest diameter was recorded. Other measurements obtained include femur length, abdominal circumference biparietal diameter, head circumference, fetal weight (FW), and GA.

Results: DFOC increased with GA. A strong positive relationship was observed between DFOC and GA with a correlation coefficient of r = 0.85. DFOC also increased with FW with a correlation coefficient of r = 0.83. The equation (GA = 30.84 + [1.25 × DFOC in mm]) relates GA to DFOC.

Conclusion: The diameter of the distal femoral epiphyseal secondary ossification center is a useful parameter for estimating GA and assessment of fetal maturity in the third trimester.

Keywords: Diameter, epiphyseal, fetal, gestational age, maturity, ossification, ultrasound