Ultrasonographic identification of fetal lower extremity epiphyseal ossification centers.

The reliability of the sonographic identification of the fetal distal femoral epiphyseal ossification center (DFE) and the proximal tibial epiphyseal ossification center (PTE) in the estimation of gestational age (GA) was assessed in 84 singleton pregnancies. We used the presence of a DFE to indicate a GA greater than or equal to 33 weeks, and this method was 95% sensitive, 95% specific, and accurate overall in 95% of a selected cohort of 61 cases. In the same cohort, the presence of the PTE was highly predictive (accuracy of a positive prediction 95%) of a GA greater than or equal to 35 weeks. Ultrasonographic evaluation of fetal lower extremity epiphyseal ossification centers is a promising technique for the estimation of GA during the last trimester of pregnancy.