PURPOSE: to evaluate the embryo's volume (EV) between the seventh and the tenth gestational week, through tridimensional ultrasonography. METHODS: a transversal study with 63 normal pregnant women between the seventh and the tenth gestational week. The ultrasonographical exams have been performed with a volumetric abdominal transducer. Virtual Organ Computer-aided Analysis (VOCAL) has been used to calculate EV, with a rotation angle of 12º and a delimitation of 15 sequential slides. The average, median, standard deviation and maximum and minimum values have been calculated for the EV in all the gestational ages. A dispersion graphic has been drawn to assess the correlation between EV and the craniogluteal length (CGL), the adjustment being done by the determination coefficient (R²). To determine EV's reference intervals as a function of the CGL, the following formula was used: percentile=EV+K versus SD, with K=1.96. RESULTS: CGL has varied from 9.0 to 39.7 mm, with an average of 23.9 mm (±7.9 mm), while EV has varied from 0.1 to 7.6 cm³, with an average of 2.7 cm³ (±3.2 cm³). EV was highly correlated to CGL, the best adjustment being obtained with quadratic regression (EV=0.2-0.055 versus CGL+0.005 versus CGL²; R²=0.8). The average EV has varied from 0.1 (-0.3 to 0.5 cm³) to 6.7 cm³ (3.8 to 9.7 cm³) within the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval, while CGL, only 4.4 times. CONCLUSIONS: EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth week of gestation.
Embryonic structures; Crown-rump length; Reference values; Pregnancy trimester first; Imaging; three-dimensional
