Sonographic identification and measurement of the epiphyseal ossification centers as markers of fetal gestational age

Purpose. This study was conducted to verify the predictive value of epiphyseal ossification center measurements in estimating gestational age. Methods. Women with singleton pregnancies of 30–40 weeks gestation (n = 377) were enrolled in this prospective study. The distal femoral, proximal tibial, and proximal humeral ossification centers were identified and measured. A nomogram of fetal bone development was created using the sum of the three diameters. Results. Gestational age correlated well with the diameters of the distal femoral and the proximal tibial epiphyseal ossification centers but even better with the sum of the three ossification centers. Positive predictive values of the fetus having gestational age of at least 37 weeks when the sum of the three centers was 7, 11, and 13 mm were 82%, 94%, and 100%, respectively. A nomogram was created using the sum of the ossification centers for 30–40 weeks' gestational age. Conclusions. Ultrasonographic visualization of the epiphyses ossification centers may be a useful marker of fetal gestational age. © 2005 Wiley Periodicals, Inc. J Clin Ultrasound 33:394–400, 2005