ESTIMATION OF GESTATIONAL-AGE BY TRANSVAGINAL SONOGRAPHIC MEASUREMENTOF GREATEST EMBRYONIC LENGTH IN DATED HUMAN EMBRYOS

A prospective descriptive study was carried out to establish reference values for gestational age assessment in the first trimester by measu ring embryonic length in dated human embryos, by using transvaginal ul trasound. In 160 pregnant women who had undergone assisted reproductiv e procedures, 139 singleton embryos and 46 embryos from 21 multiple pr egnancies were studied between the 35th and 98th day after the last me nstrual period. Transvaginal ultrasound examination, including inspect ion of embryonic structures and measurement of greatest embryonic leng th (L), was performed in these women. Estimation of gestational age (t ) by measurement of L in singletons is best described by the equation t = 35.72 + 1.082L(1/2) + 1.472L - 0.09749L(3/2). Mean 95% confidence interval and 95% prediction interval were 4.3 and 9.3 days, respective ly. There was no significant change in the estimation curve when multi ple measurements in singletons were taken nor when embryos from multip le pregnancies were measured. Accuracy of embryonic age estimation fro m a single measurement of greatest embryonic length was evaluated.