Sonographic assessment of the distal femoral and proximal tibial ossification centers in the prediction of pulmonic maturity in normal women and women with diabetes

Abstract

A noninvasive method for the assessment of fetal pulmonic maturity via the sonographic characterization of fetal distal femoral and proximal tibial epiphyseal ossification centers was evaluated. The study population included 82 patients in the third trimester of pregnancy, 47 of whom had uncomplicated gestations, while 35 had insulin-dependent diabetes. In uncomplicated pregnancies a distal femoral epiphysis measuring ≥3 mm in the axial plane or the sonographic identification of a proximal tibial epiphysis of any dimension correlated with pulmonic maturity. The combination of a distal femoral epiphysis ≥3 mm and the presence of a proximal tibial epiphysis was highly correlated with a lecithin/sphingomyelin ratio ≥2:1 (sensitivity 100%, specificity 63%, negative predictive value 100%, and false-negative rate 0%). The Kappa value (K) for testing the agreement between ultrasound results and amniocentesis results was 0.39 (p < 0.002). In diabetic pregnancies neither a distal femoral epiphysis ≥3 mm nor a proximal tibial epiphysis of any dimension correlated precisely with the presence of phosphatidyl glycerol in the amniotic fluid. However, the combination of a distal femoral epiphysis ≥3 mm and a proximal tibial epiphysis ≥2 mm improved the prediction of phosphatidyl glycerol (sensitivity 83%, specificity 79%, negative predictive value 96%, false-negative rate 17%). The K value in this instance was 0.36 (p ≥ 0.19). It is concluded that the sonographic assessment of the distal femoral and proximal tibial epiphyses and their dimensions in the axial plane may be useful as markers for pulmonic maturity in uncomplicated pregnancies.