Gestational age determination is one of the main aims of total sonorgraphy and this is determined according to some criteria including Crown-Rump Length ( CRL). In a descriptive study T estimation of Gestational age was accomplished based on 1081 CRL determination in 977 Iranian pregnant women. Comparing this Iranian gestational age table with different American tables, Iranian embroys gestational age were about 3 days more than Americans with equal CRL. Significant of independent personal variables in these gestational age estimation is also evaluated.
