[Embryo volume estimated by three-dimensional ultrasonography at seven to ten weeks of pregnancy]

to evaluate the embryo's volume (EV) between the seventh and the tenth gestational week, through tridimensional ultrasonography.

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 12 masculine 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 (R(2)). 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.

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 cm(3), with an average of 2.7 cm(3) (+/-3.2 cm(3)). EV was highly correlated to CGL, the best adjustment being obtained with quadratic regression (EV=0.2-0.055 versus CGL+0.005 versus CGL(2); R(2)=0.8). The average EV has varied from 0.1 (-0.3 to 0.5 cm(3)) to 6.7 cm(3) (3.8 to 9.7 cm(3)) within the interval of 9 to 40 mm of CGL. EV has increased 67 times in this interval, while CGL, only 4.4 times.

EV is a more sensitive parameter than CGL to evaluate embryo growth between the seventh and the tenth week of gestation.