[en] A randomized, descriptive and prospective study was conducted in 88 pregnant between 38 and 45 weeks seen in the term consultation of 'Ramon Gonzalez Coro' Gynecology-Obstetrics Hospital from May to June, 2007 underwent biometry tests according to the proposed techniques by Hadlock and Campbell to estimate the fetal weight by ultrasound (US) using four logarithm regressive equations seven days before the birth comparing it with the weight birth A absolute and relative frequency analysis was made as well as mean and standard deviation (SD),mean comparisons and indicators to assess the formulae effectiveness