Distal femoral epiphyses ossification center diameter and third trimester gestational age in Iranian population.

OBJECTIVE The epiphyses ossification centers appear late in gestation, when traditional biometric measurements are the least accurate, and they can be useful in determining third trimesters gestational age. To evaluate fetal distal femoral epiphysis (DFE) size in various ages of gestation and establish a reference chart for Iranian population. MATERIALS & METHODS DFE diameter was measured in 1300 normal singleton pregnancies, between 28 and 40 weeks. Mean diameter in each week of gestation was evaluated. RESULTS The DFE is not visualized in 28 weeks' gestation. It appeared in a small proportion of the fetuses (5%) as early as the 29th week. DFE was detectable by ultrasonography increased dramatically to 56% at 33 weeks' reaching 94% at 36 weeks and 100% at 37 weeks gestation. CONCLUSION Ultrasonographic visualization of the distal femoral epiphyses ossification center is a useful marker of fetal third trimesters gestational age.